                    IN THE SUPREME COURT OF IOWA
                                 No. 06–1428

                            Filed February 5, 2010


BRYAN RANES,

       Appellant,

vs.

ADAMS LABORATORIES, INC.; ADAMS RESPIRATORY THERAPEUTICS;
OWL PHARMACY; FRANK REZNICEK; AMANDA MATHEWS; HY-VEE,
INC.; McKESSON CORPORATION; and MICHAEL RINALDI,

       Appellees.



       Appeal from the Iowa District Court for Appanoose County, E. Richard

Meadows, Jr., Judge.



       Plaintiff appeals and defendants cross-appeal from various rulings by

the district court in a toxic-tort case that resulted in the dismissal of the

claims. AFFIRMED.



       Curt N. Daniels, Chariton, for appellant.



       Stephen R. Eckley of Belin Lamson McCormick Zumbach Flynn, P.C.,

Des Moines, for appellee Adams Laboratories, Inc.

       Thomas H. Walton and Kristina M. Stanger of Nyemaster, Goode,

West, Hansell & O’Brien, P.C., Des Moines, for appellees Owl Pharmacy,

Frank Reznicek, and Amanda Mathews.

       Kermit B. Anderson and Stacie M. Codr of Finley, Alt, Smith,

Scharnberg, Craig, Hilmes & Gaffney, P.C., Des Moines, for appellee Hy-Vee,

Inc.
                                     2

      Patrick H. O’Neill, Jr. of O’Neill & Murphy, LLC, St. Paul, Minnesota,

and William J. Bush of Bush, Motto, Creen, Koury & Halligan, P.L.C.,

Davenport, for appellee McKesson Corporation.

      Michael H. Figenshaw of Bradshaw, Fowler, Proctor & Fairgrave, P.C.,

Des Moines, for appellee Michael Rinaldi.
                                         3

CADY, Justice.

      In this appeal from various summary judgment rulings by the district

court in a toxic-tort case involving a claim that the ingestion of prescription

medication allegedly containing phenylpropanolamine caused brain injury,

we primarily consider the admissibility of testimony from an expert witness

that the injuries allegedly suffered by the plaintiff were caused by the

ingestion of phenylpropanolamine.            The district court determined the

causation opinion by the expert witness would be inadmissible at trial and

granted summary judgment to the defendants.           On appeal, we affirm the

decision of the district court.

      I. Background Facts and Proceedings.

      Phenylpropanolamine (PPA) is a drug that was used over the course of

three decades as an ingredient in many cough and cold products, as well as

in appetite-suppressant products. It was approved by the Food and Drug

Administration (FDA) in the 1970s as safe and effective and eventually

became one of the most commonly used drug ingredients in the United

States. It was widely used in both prescription and over-the-counter drugs,

with billions of doses sold each year.

      In November 2000, the FDA notified manufacturers and distributors of

drug products containing PPA that             a recent epidemiological study,

conducted by the Yale University School of Medicine in collaboration with

the FDA and manufacturers of PPA, had found a low risk of hemorrhagic

stroke among women who used weight-loss products containing PPA. The

FDA did not initiate a drug recall in response to the study, but recommended

drug companies discontinue marketing products containing PPA. The study

found no increased risk of hemorrhagic stroke among men who used

products with PPA. It also found no increased risk among women who used

cold and cough products containing PPA, but suggested such products
                                      4

presented a possible risk for hemorrhagic stroke in women based on the

increased risk found with weight-loss products. See Walter N. Kernan, et al.,

Phenylpropanolamine and the Risk of Hemorrhagic Stroke, 343 New Eng. J.

Med. 1826, 1826–32 (2000) [hereinafter Kernan].

      The FDA recommendation was widely reported to the public by the

news media.    Most manufacturers of the drug products containing PPA

promptly responded to the announcement by discontinuing the distribution

of their products containing PPA, including Adams Laboratories, Inc. and

Adams Respiratory Therapeutics, the manufacturers of a prescription cough

and cold medicine containing PPA called “Aquatab C.” Adams also notified

distributors and customers to return the product. Adams then reformulated

Aquatab C by substituting PPA with pseudophedrine and made the new

product available in March 2001. Aquatab C was distributed for Adams by

McKesson Corporation.

      On February 4, 2002, Bryan Ranes ingested Aquatab C. He had gone

to Mercy Medical Center in Centerville with complaints of a sore throat,

congestion, and a stuffy nose.     He was seen by Dr. Michael Rinaldi, who

prescribed three medications, including Aquatab C. Ranes’ mother went to

Owl Pharmacy in Centerville to fill the Aquatab C prescription.          The

pharmacist who filled the prescription was Amanda Mathews.               The

supervising pharmacist at Owl Pharmacy was Frank Reznicek.               Owl

Pharmacy did not have Aquatab C in stock at the time, but obtained it for

Ranes from a nearby Hy-Vee Pharmacy.

      Within thirty-five minutes of ingesting a tablet of Aquatab C, Ranes

claimed he began to experience intense and excruciating pain on the left side

of his head and numbness in his left arm and left side of his head. These

symptoms, and many others, allegedly reoccurred after Ranes ingested

additional tablets of Aquatab C.
                                         5

      In the months and years that followed, Ranes was seen by a number of

physicians at a number of medical facilities both in and outside Iowa for a

growing number of symptoms and complaints.                  The complaints and

symptoms Ranes reported included convulsions, urinary incontinence,

unsteady walk, vision and hearing problems, back and chest pain, diarrhea,

altered taste and smell, muscle spasms, arm pain and weakness, tremors,

numbness, and even the sight of worms crawling out of his hands. Some of

the symptoms predated the ingestion of PPA.             Prior to Ranes’ visit with

Dr. Rinaldi, on November 14, 2001, Ranes was examined at the Centerville

Medical Clinic by Dr. Donald Fraser for multiple complaints of pain in every

body part.   The results of the examination were normal, and Dr. Fraser

believed the complaints may have been attributable to general psychiatric

problems such as hypochondriasis and chronic anxiety.

      Following Ranes’ visit with Dr. Rinaldi on February 4, 2002, Ranes

was examined by a variety of physicians. An examination at Mercy Hospital

in Des Moines on February 8, 2002, four days after Ranes was prescribed

Aquatab C, included an MRI of the brain. The MRI was unremarkable, and

the   neurological   examination    by       Dr. Paul   Babikian    was   normal.

Dr. Babikian testified he did not believe Ranes suffered from vasculitis of the

cerebral vascular system. Subsequently, on March 6, 2002, Ranes was seen

by Dr. Hala Shamsuddin, an infectious disease specialist at the University of

Iowa Hospitals and Clinics.    The accompanying neurological examination

was normal, although Dr. Shamsuddin’s records indicate Ranes may have

been suffering from somatization disorder (a multisymptomatic disorder

characterized by multiple physical complaints with no known medical

explanation) and delusions of parasitosis.        A CT scan at Mercy Medical

Center in Des Moines on March 13, 2002, was normal, with no indication of

intracranial hemorrhage.    Ranes was subjected to a multispecialty team
                                      6

evaluation conducted at Mayo Clinic in Rochester, Minnesota, from

March 25, 2002, to April 26, 2002. A CT scan of the brain was normal, and

no neurological disorder was observed by neurologist Dr. Jeffrey Britton.

Doctors could find no indication of a stroke, intracranial hemorrhage, or

seizure. An MRI, MRA, CT scan, and spinal tap conducted at St. Anthony’s

Regional Medical Hospital in Rockford, Illinois, on April 30, 2002, showed no

abnormalities.    St. Anthony’s neurosurgeon Dr. Charles Wright could not

diagnose Ranes with a neurological disorder, but his summary reported

possible significant depression.    Still unsatisfied with the results, Ranes

went to the University of Nebraska Medical Center on August 8, 2002. An

MRI of the brain and an MRA of the heart conducted at the University of

Nebraska Medical Center were normal. A neurological exam conducted at

Creighton Medical Center on September 10, 2002, was normal. Finally, on

November 11, 2003, an examination performed at Washington University

School of Medicine by Dr. Jin-Moo Lee, a stroke neurologist and assistant

professor of neurology, concluded the symptoms displayed by Ranes from

February of 2002 to date were not consistent with a stroke.           Dr. Lee

considered PPA in his analysis and ruled it out due to the absence of stroke

in Ranes’ case.

      On March 5, 2004, Ranes filed a lawsuit against multiple individuals

and corporations based on multiple legal claims, including negligence, strict

liability, fraudulent nondisclosure, breach of fiduciary duty, battery, and

infliction of emotional distress.     Underlying each legal claim was an

allegation that the ingestion of Aquatab C supplied by the defendants was

the cause of a brain stroke or other neurological event that resulted in his

myriad ailments.

      Ranes continued to seek out medical evaluations after he filed his

lawsuit. In April of 2004, Ranes was examined at the McFarland Clinic in
                                      7

Ames by Dr. Michael Kitchell, a neurologist.         Dr. Kitchell found some

indication of neurological problems, but no evidence of a stroke. Dr. Kitchell

believed, to a reasonable degree of medical certainty, that Ranes’ symptoms

were not associated with PPA. In April and May of 2005, Dr. Terry Rolan

and Dr. Dale Vaslow at the University of Missouri School of Medicine

similarly found Ranes suffered from neurologically related symptoms, but his

problems were not associated with a cerebral hemorrhage. They too did not

believe Ranes’ case was associated with PPA, but rather most likely a

“parainfectious autoimmune event leading to a brain stem encephalitis.”

Dr. Rolan also believed Ranes likely had a psychological aspect to his

problems.

      During the course of the legal proceedings, Ranes identified Dr. Mark

Thoman as an expert witness who would testify at trial in support of his

claim that his ailments resulted from a brain stroke or otherwise permanent,

progressively degenerative neurological sequelae caused by the ingestion of

Aquatab C containing PPA. Dr. Thoman is a specialist in toxicology and has

primarily practiced medicine as a pediatrician. He is not a neurologist and

has not authored any reports or articles on the effects of PPA. He is not one

of Ranes’ treating physicians and has never examined him.           Dr. Thoman

agrees that his diagnosis of vasculitis is not supported by any imaging tests

or other medical tests. Dr. Thoman diagnosed Ranes with vasculitis because

he believed Ranes’ continual signs and symptoms are consistent with the

toxic effects of PPA.    The defendants identified Dr. Michael Jacoby, a

neurologist, as one of their expert witnesses for trial. Dr. Jacoby concluded

the symptoms identified by Ranes did not result from a stroke, but were

consistent   with   a   progressive   degenerative   neurological    condition.

Dr. Jacoby agreed with other neurologists who concluded Ranes did not

suffer from vasculitis. He disagreed with Dr. Thoman’s diagnosis.
                                        8

      Defendants eventually moved for summary judgment on a variety of

grounds, including the claim that Dr. Thoman was not qualified to render an

opinion that the ingestion of PPA caused Ranes’ alleged injuries, and such

an opinion failed to satisfy the standard of reliability.           The defendants

claimed summary judgment was proper because Ranes could not establish

the causation element of any of his claims without expert opinion evidence.

The motion for summary judgment was preceded by a motion to exclude the

opinion   testimony   of   Dr. Thoman       from   trial.   Ranes    acknowledged

Dr. Thoman was the only witness who would testify at trial that the ingestion

of PPA was a cause of Ranes’ alleged injuries.              However, he claimed

Dr. Thoman was qualified to provide opinion testimony on causation, and

his opinion was reliable and admissible.

      In a detailed and well-written decision, the district court found

Dr. Thoman’s testimony on causation should be excluded from trial.            The

court found Dr. Thoman was unqualified to testify about his diagnosis that

Ranes suffered from a neurological injury. It further found the differential

diagnosis methodology used by Dr. Thoman, purporting to link PPA to the

alleged neurological injuries by Ranes, was unreliable under Iowa law and

relevant considerations. The court granted the motion to exclude his opinion

from trial and granted summary judgment for all defendants.

      Ranes appealed from the decision by the district court to exclude the

opinion testimony of Dr. Thoman and to grant summary judgment.

Defendants cross-appealed from various prior summary judgment rulings by

the district court.   On appeal, Ranes claims the district court abused its

discretion to exclude the opinion testimony of Dr. Thoman from trial and

erred in granting summary judgment.
                                      9

      II. Standard of Review.

      We review a trial court’s decision to admit or exclude expert testimony

for an abuse of discretion.   Hyler v. Garner, 548 N.W.2d 864, 868 (Iowa

1996). Thus, we will reverse a decision by the district court concerning the

admissibility of expert opinions only when the record shows “the court

exercised [its] discretion on grounds or for reasons clearly untenable or to an

extent clearly unreasonable.” State v. Maghee, 573 N.W.2d 1, 5 (Iowa 1997).

“A ground or reason is untenable when it is not supported by substantial

evidence or when it is based on an erroneous application of the law.” Graber

v. City of Ankeny, 616 N.W.2d 633, 638 (Iowa 2000). This standard applies

the same to rulings admitting and rulings denying the testimony. Gen. Elec.

Co. v. Joiner, 522 U.S. 136, 142, 118 S. Ct. 512, 517, 139 L. Ed. 2d 508, 517

(1997) (noting federal courts apply abuse-of-discretion standard in reviewing

decisions to admit or exclude expert testimony).

      We review a district court decision to grant or deny a motion for

summary judgment for correction of errors at law. Kolarik v. Cory Int’l Corp.,

721 N.W.2d 159, 162 (Iowa 2006).       We examine the record to determine

whether a material fact is in dispute and, if not, whether the district court

properly applied the law. Robinson v. Fremont County, 744 N.W.2d 323, 325

(Iowa 2008). Summary judgment is proper when the plaintiff’s claim lacks

evidence to support a jury question on an essential element of the claim.

Parish v. Jumpking, Inc., 719 N.W.2d 540, 543 (Iowa 2006).

      III. Expert Testimony on Proof of Causation in Iowa.

      Generally, we have been committed to a liberal view on the

admissibility of expert testimony. See Leaf v. Goodyear Tire & Rubber Co.,

590 N.W.2d 525, 532 (1999) (citing court’s history of maintaining liberal view

on admissibility). Our broad test for admissibility of expert testimony has

two preliminary areas of judicial inquiry that must be considered before
                                       10

admitting expert testimony. See Iowa R. Evid. 5.702. The court must first

determine if the testimony “will assist the trier of fact” in understanding “the

evidence or to determine a fact in issue.” Id. This preliminary determination

not only requires the court to consider the existence of a reliable body of

“scientific, technical, or other specialized knowledge,” but it also requires the

court to ensure the evidence is relevant in assisting the trier of fact. See

Johnson v. Knoxville Cmty. Sch. Dist., 570 N.W.2d 633, 637 (Iowa 1997)

(stating that, to be relevant, the evidence must be reliable, and reliability is

an implicit requirement of admissibility under Iowa Rule of Evidence 5.702

because “unreliable testimony cannot assist the trier of fact”); see also

Bonner v. ISP Techs., Inc., 259 F.3d 924, 929 (8th Cir. 2001) (“The rule’s

concern with ‘scientific knowledge’ is a reliability requirement, while the

requirement that the evidence ‘assist the trier of fact to understand the

evidence or determine a fact in issue’ is a relevance requirement.”). Second,

the court must determine if the witness is qualified to testify “as an expert by

knowledge, skill, experience, training, or education.” Iowa R. Evid. 5.702.

      In assessing the reliability of scientific evidence under the first area of

preliminary inquiry, we essentially utilize an ad hoc approach to decide if the

scientific area of expertise produces results that are reliable enough to assist

the trier of fact. State v. Hall, 297 N.W.2d 80, 85 (Iowa 1980) (rejecting Frye

test of general scientific acceptance).      When the scientific evidence is

particularly novel or complex, however, we have suggested that courts

consider the relevant factors identified by the United States Supreme Court

in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 593–94, 113

S. Ct. 2786, 2796–97, 125 L. Ed. 2d 469, 482–83 (1993). Leaf, 590 N.W.2d

at 532. These factors help assess reliability of expert evidence by evaluating

the scientific validity of the reasoning and methodology as applied to the

facts of the case.   Daubert, 509 U.S. at 592–93, 113 S. Ct. at 2796, 125
                                       11

L. Ed. 2d at 482; see also Bonner, 259 F.3d at 929 (recognizing the purpose

of Daubert factors). These factors are:

      (1) whether the theory or technique is scientific knowledge that
      can and has been tested, (2) whether the theory or technique
      has been subjected to peer review or publication, (3) the known
      or potential rate of error, or (4) whether it is generally accepted
      within the relevant scientific community.

Leaf, 590 N.W.2d at 533.        The target of the court’s scrutiny is on the

principles and methodologies used to reach the expert’s conclusions, not the

conclusions themselves. Daubert, 509 U.S. at 595, 113 S. Ct. at 2797, 125

L. Ed. 2d 484.

      We emphasize that the ad hoc Hall test remains our general approach

to evaluating reliability, but the rapid advancements in science and medicine

have presented particularly unique challenges for courts seeking to ensure

the integrity of scientific evidence used by juries.       This judicial role has

become increasingly difficult and complex, yet important, as the access to

and availability of sources of information and opinions continue to expand.

Thus, we encourage a more expansive judicial gatekeeping function in

difficult scientific cases.   At the same time, it follows that application of

Daubert considerations is not appropriate in cases involving “technical[] or
other specialized knowledge” because such nonscientific evidence is not as

complex.      Johnson, 570 N.W.2d at 639.       As a result, the foundational

showing of reliability for nonscientific evidence is correspondingly lower. See

id. at 637.    For example, we have previously noted the inapplicability of

Daubert to “general medical issues.”        Id. at 638 (quoting Thornton v.

Caterpillar, Inc., 951 F. Supp. 575, 578 (D.S.C. 1997)).

      In all circumstances involving expert testimony, the proponent of the

evidence has the burden of demonstrating to the court as a preliminary

question of law the witness’s qualifications and the reliability of the witness’s
                                        12

opinion. Iowa R. Evid. 5.104(a); see State v. Myers, 382 N.W.2d 91, 93 (Iowa

1986); see also McClain v. Metabolife Int’l, Inc., 401 F.3d 1233, 1238 (11th

Cir. 2005). Although it is the province of the jury to evaluate the credibility

of expert witnesses, trial courts have a well-recognized role as guardians of

the integrity of expert evidence offered at trials. See, e.g., 31A Am. Jur. 2d

Expert and Opinion Evidence § 47, at 73 (2002) (“The qualifications of an

expert witness must be carefully scrutinized by the court to guard against a

pseudolearned person or charlatan who may give erroneous testimony or

opinions without a sound foundation.” (citing Webb v. Olin Mathieson Chem.

Corp., 342 P.2d 1094, 1097 (Utah 1959))); Kumho Tire Co. v. Carmichael, 526

U.S. 137, 149, 119 S. Ct. 1167, 1174–75, 143 L. Ed. 2d 238, 251 (1999); see

also Iowa R. Evid. 5.104(a) official cmt.; Leaf, 590 N.W.2d at 534 (noting

“issues of admissibility of expert testimony will be raised prior to trial”).

      Like Daubert, the case before us is a toxic-tort case.        The proffered

testimony at issue involves complex medical issues, including the potential

biological effect of PPA on the human body and on Ranes, a corresponding

differential diagnosis, and the alternative diagnosis of a complex neurological

disease. Such testimony is certainly complex, and it has the “potential to

achieve an exaggerated impact on the fact-finding process.”             Leaf, 590

N.W.2d at 534. The facts presented are far from “general,” and unlike the

cases cited in Johnson, the methodology in this case is not “based on

practical experience and acquired knowledge,” but on a somewhat novel

scientific procedure characteristic of “scientific knowledge.” 570 N.W.2d at

638. Additionally, Daubert itself was a toxic-tort case involving a complex

issue of causation. See Daubert, 509 U.S. at 582, 113 S. Ct. at 2791, 125

L. Ed. 2d at 476. Thus, the district court’s application of relevant Daubert

considerations in preliminarily assessing the reliability of Dr. Thoman’s
                                           13

methodology was appropriate under Iowa law as an exercise of the court’s

gatekeeping function. 1

       IV. Qualification of an Expert.

       A witness is qualified to assist the jury as an expert to resolve a

disputed fact if the witness has adequate “knowledge, skill, experience,

training, or education” on the subject matter in question.                Iowa R. Evid.

5.702. All expert witnesses must be qualified in the area of their testimony

based on one of the five areas of qualification. Yet, a particular degree or

type of education is not needed. Leaf, 590 N.W.2d at 535. Moreover, an

expert does not need to be a specialist in the area of the testimony as long as

the testimony is within the general area of expertise of the witness. Mensink

v. Am. Grain, 564 N.W.2d 376, 379 (Iowa 1997). However, the qualifications

of an expert can only be properly assessed in the context of the issues to be

determined by the fact finder.

       A. Overview of Analysis. In this case, the disputed factual issue is

whether the PPA contained in Aquatab C medication caused the plaintiff’s

injuries.   The district court in this case examined the issue in terms of

“general” and “specific” causation. Courts have commonly bifurcated toxic-

tort-causation analysis into two separate but related parts:                      general

causation and specific causation.             See David E. Bernstein, Getting to

Causation in Toxic Tort Cases, 74 Brook. L. Rev. 51, 52–53 ns.4, 6 (2008)

[hereinafter Bernstein]; see also Henricksen v. ConocoPhillips Co., 605

F. Supp. 2d 1142, 1155 (E.D. Wash. 2009) (“Courts in toxic tort cases often

separate    the   causation     inquiry    into   general    causation     and    specific


       1Federal  Rule of Evidence 702 was amended following the Supreme Court’s holding
in Daubert and is consistent with Daubert’s holding. See 3 David L. Faigman, et al., Modern
Scientific Evidence: The Law and Science of Expert Testimony § 22:8 & n.2, at 127–28 (2008–
2009 ed.). Because we determine Daubert principles should apply in this case, we proceed
with our analysis using relevant authority that applies and interprets Federal Rule of
Evidence 702.
                                     14

causation.”); Anderson v. Hess Corp., 592 F. Supp. 2d 1174, 1178 (D.N.D.

2009); In re Rezulin Prods. Liab. Litig., 369 F. Supp. 2d 398, 401–02

(S.D.N.Y. 2005); Bourne ex rel. Bourne v. E.I. Dupont de Nemours & Co., 189

F. Supp. 2d 482, 485 (S.D. W. Va. 2002); 3 David L. Faigman, et al., Modern

Scientific Evidence: The Law and Science of Expert Testimony § 21:2 & n.1, at

8 (2008–2009 ed.) [hereinafter Faigman] (“Cause-in-fact in toxic tort cases is

usually thought of as two separate issues: general causation and specific

causation.”). General causation is a showing that the drug or chemical is

capable of causing the type of harm from which the plaintiff suffers.

Mary Sue Henifin, et al., Reference Guide on Medical Testimony, in Reference

Manual on Scientific Evidence 439, 444 (Fed. Judicial Ctr. 2d ed. 2000)

[hereinafter Henifin].   Specific causation is evidence that the drug or

chemical in fact caused the harm from which the plaintiff suffers. Id. One

scholar has traced American courts’ usage of the bifurcated causation

analysis to a 1983 Agent Orange case.            See Joseph Sanders, The

Controversial Comment C: Factual Causation in Toxic-Substance and Disease

Cases, 44 Wake Forest L. Rev. 1029, 1048 n.5 (2009) (referring to In re

“Agent Orange” Prod. Liab. Litig., 570 F. Supp. 693, 695 (E.D.N.Y. 1983)).

The Third Restatement of Torts has recognized this relatively recent common

practice as a “device[] to organize a court’s analysis” and not as additional

elements of the tort. Restatement (Third) of Torts: Liability for Physical and

Emotional Harm § 28 cmt. c, at 405 (2010).         The Restatement authors

supplement their explanation by asserting factual causation is a necessary

element in every tort case; the “general and specific” language has simply

become more prevalent in toxic-tort cases.     See id. at 402 (“The special

problem in these cases, however, is proving the connection between a

substance and development of a specific disease. In all of these cases, the

requirement to prove factual causation remains the same[.]”). The primary
                                        15

difference between toxic-tort cases and other types of tort cases is that, in

nontoxic-tort cases, both general and specific causation are often easily

proven with the same evidence. Id. (noting when a plaintiff is injured in an

automobile accident, for example, “potential causal explanations other than

the collision are easily ruled out [i.e., specific causation]; common experience

reveals that the forces generated in a serious automobile collision are

capable of causing a fracture [i.e., general causation]”).

         This bifurcated analysis has not been explicitly used as the standard

in Iowa. However, due to its general acceptance among scholars and courts

of other jurisdictions, as well as the relative ease of application the analysis

offers to courts examining complex issues of causation, we believe it is

appropriate for courts to use the bifurcated causation language in toxic-tort

cases.     In the toxic-tort case before us, both types of causation must be

proven, and expert medical and toxicological testimony is unquestionably

required to assist the jury.    Consequently, Ranes offered the testimony of

Dr. Mark Thoman to not only show the effects that PPA is capable of

producing, but also that the PPA contained in Aquatab C actually caused the

neurological injuries alleged by Ranes.

         The relevant expert or experts on causation in toxic-tort cases must be

qualified to testify competently to both general and specific causation. See

Hyler, 548 N.W.2d at 868 (recognizing “[t]he witness must be qualified to

answer the particular question propounded”).          Yet, we have previously

determined “there is no requirement that the expert be able to express an

opinion with absolute certainty.      A lack of absolute certainty goes to the

weight of the expert’s testimony, not to its admissibility.” Johnson, 570

N.W.2d at 637 (citation omitted). Thus, the plaintiff’s expert must only be

qualified to offer a theory of causation for the jury’s consideration, not

absolute certainty. There must be evidence that would permit a reasonable
                                        16

person to conclude the drug probably caused the injury claimed. With this

in mind, we turn to consider the “knowledge, skill, experience, training or

education” of Dr. Thoman.

      B. Qualification of Dr. Thoman.              Dr. Thoman is a toxicologist.

Toxicologists study the nature, effects, and detection of poisons and

specialize in the treatment of poisoning.      Commonly accepted traits of a

qualified expert in toxicology include a degree in toxicology (a recently

developed postgraduate program at many universities), certification by the

American Board of Toxicology, and membership in professional toxicological

organizations, such as the Academy of Toxicological Sciences. Bernard D.

Goldstein & Mary Sue Henifin, Reference Guide on Toxicology, in Reference

Manual on Scientific Evidence 401, 415–17 (Fed. Judicial Ctr. 2d ed. 2000)

[hereinafter Goldstein & Henifin].

      Dr. Thoman appears to be qualified to testify about the effects of PPA

on the human body, including common symptoms of PPA poisoning, and

whether   those    effects   appeared   in   the    plaintiff’s   medical   records.

Dr. Thoman holds a medical degree, is certified by the American Board of

Medical Toxicology, and is a member of a variety of national toxicology

associations.     The record also reflects that Dr. Thoman has extensive

experience in the practice of toxicology.      Although Dr. Thoman has not

personally conducted a study involving PPA, it is the commonly accepted

practice of toxicologists to review the relevant research literature and

treatises before rendering an expert opinion. See Goldstein & Henifin at 415.

Dr. Thoman testified that he reviewed numerous case studies in medical

journals before arriving at his conclusion. Thus, the district court did not

abuse its discretion by concluding Dr. Thoman was qualified to render an

opinion on general causation, and we proceed to consider whether
                                      17

Dr. Thoman was also qualified to opine that PPA probably caused the

specific harm alleged in this case.

      The district court found Dr. Thoman was not qualified to testify that

PPA caused Ranes’ specific injuries because Dr. Thoman is not a neurologist,

and he purported to include a neurological diagnosis as the foundation of his

opinion. The district court considered Dr. Thoman’s testimony as an offer of

proof that Ranes suffered from vasculitis. However, we believe the inquiry is

narrower.    Although Dr. Thoman is not a specialist in neurology, he may

nevertheless be qualified to offer an expert opinion on the cause of Ranes’

alleged injury if he otherwise has adequate knowledge, skill, experience, or

training that would aid the jury in deciding if Ranes’ injuries were in fact

caused by PPA. An expert’s qualification “should always relate to his or her

background, education, and experience, rather than to a label which may be

applied to a profession or trade.”     31A Am. Jur. 2d Expert and Opinion

Evidence § 41, at 66–67 (2002).       Indeed, our rule of evidence does not

include a requirement for how the qualifications to testify should be

obtained, and our previous cases have held “[t]he criteria for qualifications

under rule 702 . . . are too broad to allow distinctions based on whether or

not a proposed expert belongs to a particular profession or has a particular

degree.”    Hutchison v. Am. Family Mut. Ins. Co., 514 N.W.2d 882, 887–88

(Iowa 1994).     Once qualified adequately as a toxicologist by education,

background, and experience, the expert may render an opinion on specific

causation by applying a scientifically valid methodology to the facts of the

case. See Goldstein & Henifin at 419. Thus, Dr. Thoman is not unqualified

to give an opinion on specific causation in this case solely because he is not

a neurologist.

      The evidence in this case showed Dr. Thoman has read literature on

the effects that PPA potentially has on the human brain.        Dr. Thoman’s
                                        18

clinical experiences as a physician and toxicologist have generally made him

familiar with the biological effects of sympathomimetics such as cocaine,

amphetamine,    and   PPA.     As   a    board-certified   medical   toxicologist,

Dr. Thoman was certainly qualified to discuss the potential effects of PPA on

the human body, but Dr. Thoman was also qualified to offer an analysis of

PPA’s potential effects on Ranes.   Consequently, we next turn to consider

whether Dr. Thoman’s analysis in this case was scientifically sound.           In

doing so, we must decide whether the district court abused its discretion by

excluding Dr. Thoman’s testimony as unreliable.

      V.   Reliability of the Scientific Knowledge of a Qualified Expert.

      Dr. Thoman offered a differential diagnosis to show both general and

specific causation in this case.        In order to determine whether this

differential diagnosis is reliable, we must first decide whether a sufficiently

reliable scientific foundation existed for Dr. Thoman’s decision to “rule in”

PPA as a potential cause of Ranes’ alleged injuries. We begin by scrutinizing

Dr. Thoman’s opinion on general causation because his differential diagnosis

rests on the necessary assumption that the underlying methodology used to

rule PPA in as a cause is sound. Failure to reliably “rule in” the defendant’s

drug as a cause of the injuries in a particular case is commonly fatal to

plaintiffs seeking to survive summary judgment in toxic tort cases.           See

Faigman § 21:2, at 9 (“[A] failure to lay a sufficient general causation

predicate is often cited as grounds for excluding an expert’s differential

diagnosis testimony.”); id. § 21:6, at 25 (“The ‘rule in before ruling out’

position of Cavallo [v. Star Enter., 892 F. Supp. 756 (E.D. Va. 1995), aff’d in

relevant part, 100 F.3d 1150, 1159 (4th Cir. 1996)] presumes that at least in

toxic tort cases a differential diagnosis, no matter how well done, can rarely,

by itself, prove general causation.”); see also Hollander v. Sandoz Pharms.

Corp., 289 F.3d 1193, 1210–11 (10th Cir. 2002) (“In order to ‘rule in’ Parlodel
                                       19

as a scientifically plausible cause of Ms. Hollander’s stroke, the Hollanders’

experts would need to present reliable evidence that the drug can cause

strokes . . . .”); Meister v. Med. Eng’g Corp., 267 F.3d 1123, 1130 (D.C. Cir.

2001) (no causal link between silicone breast implants and scleroderma,

thus no liability); Raynor v. Merrell Pharms. Inc., 104 F.3d 1371, 1376 (D.C.

Cir. 1997) (“[T]estimony on specific causation had legitimacy only as follow-

up to admissible evidence that the drug in question could in general cause

birth defects.    That first step, establishing a link between Benedectin and

human birth defects (general causation) is missing here.”); Kolesar v. United

Agri Prods., Inc., 412 F. Supp. 2d 686, 697 (W.D. Mich. 2006) (explaining

that a valid differential diagnosis entails excluding alternative causes of a

disease to arrive at a conclusion); Coastal Tankships, U.S.A., Inc. v.

Anderson, 87 S.W.3d 591, 609–10 (Tex. App. 2002) (“In the toxic-tort

context, a plaintiff must establish general causation for a differential

diagnosis to be relevant to show specific causation.”). Due to the inherent

logic in the “rule in before ruling out” approach, and the intricate ties in this

case between Dr. Thoman’s differential diagnosis of causation and proof of

general causation, we will begin our reliability analysis with a discussion of

general causation.

       A. Overview of Reliability Under General Causation Analysis. Rule

5.702 places a gatekeeping function with the district court to “[ensure] that

evidence submitted to the jury meets [the rule’s] criteria for relevance and

reliability.”   Bonner, 259 F.3d at 929.     The evaluation of reliability is a

factually sensitive analysis.   Id.   The amount of foundation necessary to

show reliability necessarily increases with the complexity of the case and the

corollary likelihood the expert testimony will have a substantial impact on

the fact finder.    Johnson, 570 N.W.2d at 637.      Yet, reliability should be

assessed by examining the expert’s “ ‘principles and methodology, not . . .
                                         20

the conclusions that they generate.’ ”        Bonner, 259 F.3d at 929 (quoting

Daubert, 509 U.S. at 595, 113 S. Ct. at 2797, 125 L. Ed. 2d at 484).         As

applied to this case, the expert’s methodology underlying his opinion must

be evaluated both as to general and specific causation. See id. at 931–32

(reviewing expert’s methodology in arriving at conclusion with respect to

both types of causation). Thus, we will review the reliability of Dr. Thoman’s

methodology in reaching a conclusion on each type of causation.

      B. Reliability of Dr. Thoman’s Testimony.           In order to establish

general causation, Ranes must show PPA is capable of causing the injuries

he claims.   See Henifin at 469 (“The third step [in determining external

causation] is to demonstrate that the medical and scientific literature

provides   evidence   that   in   some   circumstances    the   exposure   under

consideration can cause the outcome under consideration.           This step is

synonymous with establishment of general causation.”). Problems can often

arise in showing reliability of causation testimony in toxic-tort cases because

of the “uncertainties concerning the mechanisms by which medical

conditions develop from [exposure to a toxic substance] and the difficulties of

ruling out other potential causes of those conditions.” 4 Jack B. Weinstein

& Margaret A. Berger, Weinstein’s Federal Evidence § 702.06(c)(i), at 702–

127 (Joseph M. McLaughlin ed., 2d ed. 2009).           When no scientific basis

exists for conclusively identifying causation between the plaintiff’s medical

condition and the alleged wrong, medical experts recognize certain protocols

to permit an opinion on causation to be expressed in terms of a reasonable

medical certainty. Id. at 702–128.

      The proffered evidence by Ranes on general causation was based

primarily on case studies and case reports on the association between PPA

and incidents of diagnosed stroke or vasculitis. Dr. Thoman did not conduct

his own study on the effects of PPA on Ranes or on any other patients.
                                     21

Thus, with Daubert considerations in mind, we assess the validity of

Dr. Thoman’s methodology based on the research and literature available to

him.

       The district court examined whether Dr. Thoman’s theory is “scientific

knowledge that can and has been tested” and whether the theory or

technique “has been subjected to peer review or publication.” We have also

highlighted one particular factor in our previous case law:         “proof of

acceptance of the theory or technique in the scientific community.”      Leaf,

590 N.W.2d at 534. As the district court correctly points out, there is no

dispute Dr. Thoman’s personal theory that PPA can cause progressive,

degenerative neurological symptoms, based on studies suggesting PPA may

cause risk of stroke and vasculitis, has not been published or subjected to

peer review.      The main considerations under scrutiny are whether

Dr. Thoman’s theory “is scientific knowledge that can and has been tested”

and whether his methodology is generally accepted in the fields of medicine

and toxicology.   Normally, general causation can be satisfied in part by

medical and scientific literature supporting the conclusion that a drug is

capable of causing the relevant injury. See Henifin at 469. However, the

scientific value of various studies must be considered to fully understand the

evidence an expert is justified in relying upon in any particular causation

methodology.

       Dr. Thoman relied on two different types of studies in formulating his

general causation opinion:    a case-control study and case reports (also

referred to as “case studies”). Dr. Thoman did not use any clinical trials. In

epidemiological parlance, clinical trials are considered the “gold standard”

for determining the relationship between a drug and a health outcome. See

Michael D. Green et al., Reference Guide on Epidemiology, in Reference

Manual on Scientific Evidence 333, 338 (Fed. Judicial Ctr. 2d ed. 2000). In
                                       22

clinical trials, participants are divided into two groups: one group is exposed

to the substance under study and the other group, a “control group,” is left

unexposed. Id. Yet, clinical trials are not commonly available for the study

of harmful toxins because ethical constraints preclude it.       See id. at 339

(observing “[w]hen an agent’s effects are suspected to be harmful, we cannot

knowingly expose people to the agent”).           Thus, medical experts are

accustomed to using other methods of arriving at a causation opinion.

      One such alternative method is to consider relevant case-control

studies.   Case-control studies “measure and compare the frequency of

exposure in the group with the disease (the ‘cases’) and the group without

the disease (the ‘controls’). . . . [C]ase-control studies begin with individuals

who are selected based on whether they have the disease or do not have the

disease . . . .” Id. at 340. Experts assess the validity of using these studies

in a particular case according to the studies’ direct relevance to the injuries

alleged in a case and according to the studies’ known sources of error. See

id. at 354; see also In re Rezulin, 369 F. Supp. 2d at 426 (noting “ ‘[e]ven if

an expert’s proposed testimony constitutes scientific knowledge, his or her

testimony will be excluded if it is not scientific knowledge for purposes of the

case’ ” (quoting In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 743 (3d Cir.

1994))).

      Dr. Thoman used one case-control study—the Yale study in the

New England Journal of Medicine—in his general causation analysis.           The

study concluded PPA was likely to cause hemorrhagic stroke in women, but

also concluded “[a]n analysis in men showed no increased risk of

hemorrhagic stroke in association with the use of cough or cold remedies

containing phenylpropanolamine.” Kernan at 1826. Dr. Thoman reasoned,

from this study, PPA can likely cause stroke, and since Ranes likely suffered

a “stroke-like event,” this study tended to show a relevant causal connection.
                                      23

This study is simply not relevant to the case before us. It excludes men and

only references hemorrhagic stroke in women. Moreover, the study does not

describe an injury following PPA ingestion called “stroke-like event.” In fact,

stroke does not appear to be the injury at issue in this case at all.

Dr. Michael   Jacoby,   a   neurologist,   testified   “[t]here   is   no   medically

recognized ‘death-like’ condition of brain cells . . . [and] there is no such

recognized medical condition as a stroke-like event . . . .”            Dr. Thoman

acknowledged he deferred to neurologists to determine whether a stroke in

fact occurred, and all eight neurologists involved with Ranes’ case refuted

the diagnosis of stroke.      Dr. Thoman did not attempt to explain his

extrapolation from the study’s reference to “stroke” to Ranes’ so-called

“stroke-like event,” involving a progressive neurologic degeneration.             As

such, this case-control study is not relevant to the injuries alleged in this

case and cannot be the basis of any general causation opinion.

      Next, the record shows Dr. Thoman relied heavily upon several case

reports from various sources. Case reports are reports in medical journals

describing clinical events involving one individual or a few individuals. See

Henifin at 474. The reports may show, among other things, an association

between a specific exposure and a disease or injury. Id. Case report results

are often confirmed or dismissed later by clinical trials or case-control

studies. Id. Because unconfirmed case reports lack controls, they do not

provide as much useful information to medical experts in directly assigning

causation as controlled epidemiological studies.        Id. at 475.     As a result,

“[c]ausal attribution based on case studies must be regarded with caution.”

Id. As the eleventh circuit has articulated,

      case reports are merely accounts of medical events. They reflect
      only reported data, not scientific methodology. . . .

            . . . Even these more detailed case reports, however, are
      not reliable enough, by themselves, to demonstrate the causal
                                       24
      link the plaintiffs assert that they do because they report
      symptoms observed in a single patient in an uncontrolled
      context. . . . As such, while they may support other proof of
      causation, case reports alone ordinarily cannot prove causation.

Rider v. Sandoz Pharms. Corp., 295 F.3d 1194, 1199 (11th Cir. 2002).

      Many courts, like the eleventh circuit, have found expert opinions

based in part on case studies and reports and in part by other data and
individual research to be reliable. See id.; see also Goldstein & Henifin at

475 & n.132. On the other hand, courts generally conclude, as the district

court concluded in this case, that a bare analogy from case reports to the

injuries alleged in a particular case is unreliable. See McClain, 401 F.3d at

1253–54; In re Rezulin, 369 F. Supp. 2d at 426–27; Lennon v. Norfolk & W.

Ry., 123 F. Supp. 2d 1143, 1151–53 (N.D. Ind. 2000).          While there is no

requirement that a medical expert cite published epidemiological studies on

general causation to make a reliable conclusion, the methodology used by

the expert becomes suspect when it is only supported by case reports of

limited use to the medical field.     See Bloomquist v. Wapello County, 500

N.W.2d 1, 5 (1993) (noting “while epidemiological evidence is helpful, it

should not be held to be an absolute requirement in establishing

causation”); see also Bonner, 259 F.3d at 929–31 (noting the general rule

and finding the expert’s subsequent reliance on case reports in addition to

other facts reliable). We likewise believe it is important to the integrity of

expert evidence presented to a jury that case reports are not given more

weight in the courtroom than they would ordinarily be given in the medical

field. Although generally “ ‘the factual basis of an expert opinion goes to the

credibility of the testimony, not the admissibility,’ . . . if an expert’s opinion

is ‘so fundamentally unsupported . . . it can offer no assistance to the jury

. . .,’ ” it must be excluded. Hose v. Chicago Nw. Transp. Co., 70 F.3d 968,

974 (8th Cir. 1995) (quoting Loudermill v. Dow Chem. Co., 863 F.2d 566, 570
                                      25

(8th Cir. 1988)); see also Laurie Kratky Dorè, 7 Iowa Practice: Evidence

§ 5.703:1, at 625 (2009) (“Without reference to some facts pertinent to the

matter in issue, an expert cannot state an opinion that will be of assistance

to the trier of fact.”). Here, the case reports used by Dr. Thoman to support

general causation were not only unaccompanied by additional reliable

methodology and facts, but the disorders addressed in the case reports

described symptoms different from the symptoms experienced by Ranes.

Thus, we proceed to examine these deficiencies.

        Dr. Thoman attempted to support the case study conclusions by

offering his own clinical experience with children and some adults in whom

exposure to PPA caused headaches, photophobia, ataxia, chest pain,

weakness, and inappropriate behavior.       Yet, in Dr. Thoman’s experience,

these     symptoms   disappeared   when    the   patient   stopped   taking   the

substance.     In contrast, Ranes’ symptoms not only continued after he

stopped taking Aquatab C, but multiplied. Dr. Thoman made no attempt to

offer an independent analysis in tandem with the case study to explain the

differences between Ranes’ symptoms and existing cases of PPA-induced

injury.    Instead, Dr. Thoman continuously testified there were no existing

case reports that tended to show a patient with or without a diagnosis of

vasculitis had the same symptomology as Ranes. This analysis amounts to a

bare case report analogy, with no accompanying facts or circumstances to

support the analogy. Moreover, if Dr. Thoman had taken his opinion in this

case to a medical journal for publication, it would be in the form of another

case report related to PPA, not a clinical trial or case-control study.       See

McClain, 401 F.3d at 1254. Reasonable medical experts would not rely upon

the presented anecdotal information, standing alone, as providing a

sufficient scientific basis to support the view that PPA causes vasculitis in

males in light of the lack of controls, details, and further analysis.
                                             26

Similarly, courts should not admit opinions based upon unreliable

methodology.

       Dr. Thoman sought to sidestep criticism that the case reports

described disorders dissimilar to the disorder suffered by Ranes by

diagnosing Ranes with vasculitis and then connecting this diagnosis with

those particular case reports tending to show a specific instance of vasculitis

may have been caused by the ingestion of PPA.                  This analysis, of course,

does not aid in establishing the reliability of the case reports to support

causation because a diagnosis of a disorder does not constitute additional

evidence of causation of the disorder. A diagnosis of vasculitis relates to a

description of the disorder, not additional scientific methodology or evidence

to make the case reports reliable proof of a causal link between PPA and

vasculitis. In the end, Dr. Thoman merely described his own isolated case

report. He does not advance the reliability of his opinion that PPA can cause

vasculitis.

       Moreover, the diagnosis of vasculitis made by Dr. Thoman gives rise to

additional    concerns      normally     addressed      in   the   analysis     of   specific

causation. 2 Even assuming there was reliable evidence that PPA can cause

vasculitis, such an opinion is relevant only if Dr. Thoman meets the
foundational standards to diagnosis Ranes with vasculitis. If PPA can cause

vasculitis in men, then part of specific causation requires a showing that the



       2In  toxic-tort cases, both general and specific causation address the link between a
drug and a disorder. The evidence to support general causation, however, normally focuses
on the science that shows a causal connection between drugs and disorders in people. In
turn, this science further tends to define the scope or range of disorders linked to the drug.
Thus, if reliable science supports a causal connection between a specific drug and a
particular brain disorder, the plaintiff completes the general causation analysis by alleging
he or she suffered from that brain disorder. The evidence to support specific causation
generally focuses on facts specific to a particular case that show a drug was an actual cause
of the disorder suffered by the plaintiff. Thus, supporting evidence not only pertains to the
cause of disorder, but also relates to a diagnosis of the disorder.
                                        27

disorder suffered by the plaintiff is vasculitis. The diagnosis of vasculitis by

Dr. Thoman is critical to the analysis because he was the only physician to

diagnose Ranes with the disorder.

      C. Reliability     Under     Specific    Causation     Analysis.     Specific

causation in toxic-tort cases examines whether the toxin at issue could have

reasonably caused the plaintiff’s specific alleged injuries.              As noted

previously, a differential diagnosis in a proper specific causation analysis

assumes the toxin at issue is capable of causing the outcome under

consideration. See Goldstein & Henifin at 469–70. A differential diagnosis

involves “ruling in” specific causes, followed by a process of elimination, and

“the final suspected ‘cause’ remaining after this process of elimination must

actually be capable of causing the injury.”          Cavallo, 892 F. Supp. at 771.

Since Ranes has failed to reliably show PPA is an external factor to be “ruled

in” to a differential causation diagnosis, it follows he cannot establish PPA

caused his specific injuries.

      Additionally, even assuming PPA could be “ruled in” to a differential

causation diagnosis to support the specific causation of the claimed

disorder, Ranes must first show he suffered from the disorder alleged.

Although doctors are ordinarily qualified to render a medical diagnosis, both

the parties presented evidence that vasculitis is a rare disease that is

difficult to diagnose.    In the context of this complex toxic-tort case, and

mindful of the complicated nature of the alleged disease at issue, we proceed

to analyze the admissibility of Dr. Thoman’s diagnosis testimony under our

legal principles and the relevant Daubert considerations.

      1. Qualification of Dr. Thoman as a diagnosing medical expert.            In

Dr. Thoman’s deposition, he concluded Ranes suffered from PPA-induced

vasculitis   because     his    symptoms      were    consistent   with   symptoms

characteristic of vasculitis. Vasculitis is the inflammation of blood vessels.
                                             28

Dr. Jacoby testified vasculitis is “a very rare disorder,” complex and difficult

to   diagnose,    with    symptoms       that     are   often     fatal   if   left     untreated

appropriately. As we have said before, the ability of a witness to testify is

determined according to the specific issue presented. Tappe ex rel. Tappe v.

Iowa Methodist Med. Ctr., 477 N.W.2d 396, 402 (Iowa 1991). The plaintiff

bears the burden of proving the expert is qualified under rule 5.702. Myers,

382 N.W.2d at 93.

       Here, the issue is whether Ranes suffered from the effects of vasculitis.

The plaintiff presented no evidence that Dr. Thoman has knowledge, skill,

experience, training, or education suitable to an expert testifying about a

neurological diagnosis of a complex nature.               Dr. Thoman is undisputedly

neither a qualified neurologist, nor one of Ranes’ treating physicians. The

diagnosis of vasculitis does not fall within his general area of expertise. See

Hunter v. Bd. of Trs., 481 N.W.2d 510, 520 (Iowa 1992) (“[T]he witness need

not be a specialist in the particular area of testimony so long as the

testimony     falls   within     the    witness[’s]     general     area       of     expertise.”).

Additionally, no evidence was offered to reveal sufficient experience,

knowledge, or training to show Dr. Thoman was qualified to render such a

complex diagnosis.

       2. Reliability of methodology used by Dr. Thoman.                            Dr. Thoman’s

purported methodology in reaching his diagnosis was also unreliable.                            In

making a clinical diagnosis, it is common practice among medical experts to

perform a differential diagnosis 3 by developing a “list of all the possible

       3The   phrase “differential diagnosis” is used by the medical profession to refer to two
different processes: the process of determining the disease responsible for causing a
particular patient’s symptoms in a specific case, and the process of determining the cause of
a diagnosed disease in a specific case. Henifin at 443. Some courts and expert witnesses
use the phrase “differential etiology” to identify the process of determining causation and
“differential diagnosis” for the process of diagnosing disease because the term “etiology”
refers to the cause of disease, but this distinction is not by the medical profession. Id. The
same scientific process may be used in both general and specific causation analyses, and
                                           29

diseases that could produce the observed signs and symptoms,” then

comparing the expected clinical findings for each of the possible diseases

with the patient’s actual symptoms and test results.                 See Goldstein &

Henifin at 463. Although the process of medical diagnosis is not an exact

science, there does appear to be a medically accepted method of arriving at a

diagnosis in any given case.         See generally id. at 463–64 (describing the

process for clinical diagnosis). Probabilities of disease are combined with a

physician’s “knowledge of the frequency of signs and symptoms in a given

disease and competing diseases to progressively modify and ultimately arrive

at their view of the likelihood of the disease under consideration.” See id. at

467.

       In this case, Dr. Thoman departed from a recognized medical process

of diagnosing disease. First, evidence was presented to show Dr. Thoman

did not consider the variety of diseases that tend to mimic the symptoms of

vasculitis. Instead of considering the negative imaging results for vasculitis,

Dr. Thoman dismissed all neurological tests performed over the course of

three years as faulty. Of course, all diagnostic imaging tests that would have

likely revealed inflammation to support the vasculitis, including an

angiogram, were performed on Ranes and showed no abnormalities. Yet, a

diagnosis of vasculitis, while seemingly far-fetched, is not impossible.

Indeed, diagnostic imaging tests are known to be limited by potential error.

See Goldstein & Henifin at 458.           Dr. Vaslow testified that “standard MRI

sequences may fail to detect acute stroke in 10 to 20 percent of patients.”

MRIs with diffusion and profusion weighted imaging are more accurate at

detecting stroke. While Ranes was tested with an MRI machine within days


here, we use it to refer to the process by which Dr. Thoman arrived at his diagnosis of
vasculitis, a disease. We use the phrase “differential diagnosis” in this opinion the same
way the medical profession uses it in order to maintain clarity and consistency.
                                     30

of the first headache following prescribed dosages of Aquatab C, Dr. Vaslow

could not determine whether the machine used at that time was an MRI with

a diffusion and profusion weighted imaging. It is the plaintiff’s burden to

demonstrate it is more likely than not that the imaging technology in this

case was too inaccurate to detect Ranes’ alleged brain lesion, and such

evidence does not appear on the record.

      Notwithstanding, the state of the technology used to diagnose Ranes is

only one of many potential considerations in diagnosing a patient.

Importantly, Dr. Thoman’s diagnosis of vasculitis and subsequent brain cell

death was premised solely on Ranes’ degenerative symptoms. Dr. Thoman

did not perform a proper differential analysis to arrive at his diagnosis of

vasculitis.   Instead, Dr. Thoman summarily dismissed as many as eight

mimicking conditions due to his lack of background and experience in

diagnosing neurological diseases.     Several other neurologists, including

Dr. Babikian, dismissed vasculitis as a diagnosis in the course of their

individual differential diagnoses. In the end, the record shows Dr. Thoman

relied only on symptoms Ranes reported to tie the case reports he located to

Ranes’ case.     This analysis is clearly inconsistent with the accepted

methodology. Expert analysis that discusses only the evidence the expert

believes will advance the plaintiff’s position, and ignores a large amount of

information that calls the expert’s theory into question, cannot be considered

reliable. See In re Rezulin, 369 F. Supp. 2d at 425–26.

      Regardless of the reasons or motives for Dr. Thoman to diagnose

Ranes with vasculitis in order to reach his opinion that PPA is capable of

causing the injuries alleged by Ranes, the methodology he used to diagnose

vasculitis is contrary to the methodology described by the scientific

literature. Our standard for admission of expert evidence does not seek to

exclude scientific hypotheses merely because they are “novel” or “unusual.”
                                              31

However, “scientific knowledge” implies the opinion is based on more than

unsupported speculation. Daubert, 509 U.S. at 590, 113 S. Ct. at 2795, 125

L. Ed. 2d at 481.       Although scientists do not purport to assert facts they

believe are immutably true, “in order to qualify as ‘scientific knowledge,’ an

inference or assertion must be derived by the scientific method. Proposed

testimony must be supported by appropriate validation—i.e., ‘good grounds,’

based on what is known.” Id. The courtroom must not be an arena “for

scientific guesswork, even of the inspired sort. Law lags science; it does not

lead it.” Rosen v. Ciba-Geigy Corp., 78 F.3d 316, 319 (7th Cir. 1996). As

such, we cannot conclude the district court abused its discretion in refusing

to admit Dr. Thoman’s diagnosis of vasculitis. 4

       VI. Conclusion.

       We conclude the district court did not abuse its discretion by finding

Dr. Thoman did not practice a reliable methodology in reaching his opinion

that the ingestion of PPA was the cause of Ranes’ alleged injuries.

Consequently, Ranes failed to offer sufficient evidence to generate a factual

question for the jury on the issue of causation to support his cause of action,

and the district court properly granted summary judgment.                       Because the

summary judgment dismissed the case against all defendants, we need not
address any remaining issues in the case, and we do not consider the issues

presented in the cross-appeals by defendants.

       AFFIRMED.

       All justices concur except Wiggins, J., who takes no part.

        4Prior to submission of this case, the plaintiff offered a “Notice of Additional

Authority” for consideration. Generally, courts may consider authority outside the record in
interpreting statutes and legislative facts. However, the facts the plaintiff proposes to
include are evidentiary, not legal, in nature and will therefore be excluded from our
discussion. Even assuming the facts offered are not precluded, such evidence would not
support the plaintiff’s efforts to establish the reliability of Dr. Thoman’s methodology in this
case due to Dr. Thoman’s unqualified and unreliable process in diagnosing Ranes with
vasculitis.
