Learning to Embrace Flawed Evidence – The Avandia MDL’s Daubert Opinion

If GlaxoSmithKline (GSK) did not have bad luck when it comes to its oral anti-diabetic medication Avandia, it would have no luck at all.

On January 4, 2011, the federal judge who oversees the Avandia multi-district litigation (MDL) in Philadelphia entered an order denying GSK’s motion to exclude the causation opinion testimony of plaintiffs’ expert witnesses.  In re Avandia Marketing, Sales Practices, and Products Liab. Litig., MDL 1871, Mem. Op. and Order (E.D.Pa. Jan. 3, 2011)(Rufe, J.)[cited as “Op.”].  The decision is available on the CBS Interactive Business Network news blog, BNET

Based largely upon a meta-analysis of randomized clinical trials (RCTs) by Dr Steven Nissen and Ms Kathleen Wolski, plaintiffs’ witnesses opined that Avandia (rosiglitizone) causes heart attacks and strokes.  Because meta-analysis has received so little serious judicial attention in connection with Rule 702 or 703 motions, this opinion by the Hon. Cynthia Rufe, deserves careful attention by all students of “Daubert” law.  Unfortunately, that attention is likely to be critical — Judge Rufe’s opinion fails to engage the law and facts of the case, while committing serious mistakes on both fronts.

The Law

The reader will know that things are not going well for a sound legal analysis when the trial court begins by misstating the controlling law for decision:

“Under the Third Circuit framework, the focus of the Court’s inquiry must be on the experts’ methods, not their conclusions. Therefore, the fact that Plaintiffs’ experts and defendants’ experts reach different conclusions does not factor into the Court’s assessment of the reliability of their methods.”

Op. at 2 (internal citation omitted).

and

“As noted, the experts are not required to use the best possible methods, but rather are required to use scientifically reliable methods.”

Op. at 26.

Although the United States Supreme Court attempted, in Daubert, to draw a distinction between the reliability of an expert witness’s methodology and conclusion, that Court soon realized that the distinction is flawed. If an expert witness’s proffered testimony is discordant from regulatory and scientific conclusions, a reasonable, disinterested scientists would be led to question the reliability of the testimony’s methodology and its inferences from facts and data, to its conclusion.  The Supreme Court recognized this connection in General Electric v. Joiner, and the connection between methodology and conclusions was ultimately incorporated into a statute, the revised Federal Rule of Evidence 702:

“[I]f scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training or education, may testify thereto in the form of an opinion or otherwise, if

  1. the testimony is based upon sufficient fact or data,
  2. the testimony is the product of reliable principles and methods; and
  3. the witness has applied the principles and methods reliably to the facts.”

The Avandia MDL court thus ignored the clear mandate of a statute, Rule 702(1), and applied an unspecified “Third Circuit” framework, which is legally invalid to the extent it departs from the statute.

The Avandia court’s ruling, however, goes beyond this clear error in applying the wrong law.  Judge Rufe notes that:

“The experts must use good grounds to reach their conclusions, but not necessarily the best grounds or unflawed methods.”

Op. at 2-3 (internal citations omitted).

Here the trial court’s double negative is confusing.  The court clearly suggests that plaintiffs’ experts must use “good grounds,” but that their methods can be flawed and still survive challenge.  We can certainly hope that the trial court did not intend to depart so far from the statute, scientific method, and common sense, but the court’s own language suggests that it abused its discretion in applying a clearly incorrect standard.

Misstatements of Fact

The apparent errors of the Avandia decision transcend mistaken legal standards, and go to key facts of the case.  Some errors perhaps show inadvertence or inattention, for instance, when the court states that the RECORD trial, an RCT conducted by GSK, set out “specifically to compare the cardiovascular safety of Avandia to that of Actos (a competitor medication in the same class).  Op. at 4.  In fact, Actos (or pioglitazone) was not involved in the RECORD trial, which involved Avandia, along with two other oral anti-diabetic medications, metformin and sulfonylurea. 

Erroneous Reliance upon p-values to the exclusion of Confidence Intervals

Other misstatements of fact, however, suggest that the trial court did not understand the scientific evidence in the case.  By way of example, the trial court erroneously over-emphasized p-values, and ignored the important interpretative value of the corresponding confidence intervals.  For example, we are told that “[t]he NISSEN meta-analysis combined 42 clinical trials, including the RECORD trial and other RCTs, and found that Avandia increased the risk of myocardial infarction by 43%, a statistically significant result (p = .031).”  Op. at 5.  Ignoring for the moment that the cited meta-analysis did not include the RECORD RCT, the Court should have have reported the p-value along with the corresponding two-sided 95% confidence interval:

“the odds ratio for myocardial infarction was 1.43 (95% confidence interval [CI], 1.03 to 1.98; P = 0.03).”

Steven E. Nissen, M.D., and Kathy Wolski, M.P.H., “Effect of Rosiglitazone on the Risk of Myocardial Infarction and Death from Cardiovascular Causes,” 356 New Engl. J. Med. 2457, 2457 (2007).

The Court repeats this error later in its opinion:

“In 2007, the New England Journal of Medicine published the NISSEN meta-analysis, which combined results from 42 double-blind RCTs and found that patients taking Avandia had a statistically significant 43% increase in myocardial ischemic events. NISSEN used all publicly available data from double-blind RCTs of Avandia in which cardiovascular disease events were recorded, thereby eliminating one major drawback of meta-analysis: the biased selection of studies.”

Op. at 17.  The second time, however, the Court introduced new factual errors.  The Court erred in suggesting that Nissen uses all publicly available data.  There were, in fact, studies available to Nissen and to the public, which met Nissen’s inclusion criteria, but which he failed to include in his meta-analysis.  Nissen’s meta-analysis was thus biased by its failure to have conducted a complete, thorough review of the medical literature for qualifying RCTs.  Furthermore, contrary to the Court’s statement, Nissen included non-double-blinded RCTs, as his own published paper makes clear.

Erroneous Interpretation of p-values

The court erred in its interpretation of p-values:

 “The DREAM and ADOPT studies were designed to study the impact of Avandia on prediabetics and newly diagnosed diabetics. Even in these relatively low-risk groups, there was a trend towards an adverse outcome for Avandia users (e.g., in DREAM, the p-value was .08, which means that there is a 92% likelihood that the difference between the two groups was not the result of mere chance). “

Op. at 25 (internal citation omitted).  The p-value is, of course, the probability that results as large or larger would have been observed, given the truth of the null hypothesis that there is no difference between Avandia and its comparator medications.  The p-value does not permit a probabilistic assessment of the correctness of the null hypothesis; nor does it permit a straightforward probabilistic assessment of the correctness of the alternative hypothesis of rejecting the null hypothesis.

See Federal Judical Center, Reference Manual Scientific Evidence 2d ed. 122, 357 (2000).

Hand Waiving over Statin Use

The Court appeared to have been confused by plaintiffs’ rhetoric that statin use masked a real risk of heart attacks in the Avandia RCTs. 

“It is not clear whether statin use was allowed in the DREAM study.”

Op. at 25.  The problem is that the Court fails to point to any evidence that the use of statins differed between the Avandia and comparator arms of the RCTs.  Statins have been one of the great pharmaceutical success stories of the last 15 years, and it is reasonable to believe that today most diabetic patients (who often high blood fats) would taking statins.  At the time of the DREAM study, the prevalence of use would have been lower than today, but there was no evidence mentioned that the use was different between the Avandia and other arms of the DREAM trial.

Errors in Interpreting RCTs by Intention to Treat Analyses

For unexplained reasons, the court was impressed by what it called a high dropout rate in one of the larger Avandia RCTs:

“The ADOPT study was marred by a very high dropout rate (more than 40% of the subjects did not complete the four year follow up) and the use of statins during the trial.”

Op. at 25.  Talk about being hoisted with one’s own petard!  The high dropout rate in ADOPT resulted from the fact that this RCT was a long-term test of “glycemic control.”  Avandia did better with respect to durable glycemic control than two major, accepted medications, metformin and sulfonylurea, and thus the dropouts came mostly in the comparator arms as patients not taking Avandia required more and stronger medications, or even injected insulin.  The study investigators were obligated to analyze their data in accord with “intention to treat” principles, and so patients removed from the trial due to lack of glycemic control could no longer be counted with respect to any outcome of interest.  Avandia patients thus had longer follow-up time, and more opportunity to have events due to their underlying pathologic physiology (diabetes and diabetic-related heart attacks).

Ignoring Defense Arguments

GSK may have hurt itself by electing not to call an expert witness at the Daubert hearing in this MDL.  Still, the following statement by the Court is hard to square with opening argument given at the hearing:

“GSK points out no specific flaws or limitations in the design or implementation of the NISSEN meta-analysis”

Op. at 6.  If true, then shame on GSK; but somehow this statement seems too incredible to be true.

Ignoring the Difference between myocardial ischemic events and myocardial infarction (MI)

MI occurs when heart muscle dies as a result of a blockage in a blood vessel that brings oxygenated blood.  An ischemic event is defined very broadly in GSK’s study:

“To minimize the possibility of missing events of interest, all events coded with broadly inclusive AE terms captured from investigator reports were reviewed. SAEs identified from the trials database included cardiac failure, angina pectoris, acute pulmonary edema, all cases of chest pain without a clear non-cardiac etiology and myocardial infarction/myocardial ischemia.”

Alexander Cobitz MD, PhD, et al., “A retrospective evaluation of congestive heart failure and myocardial ischemia events in 14 237 patients with type 2 diabetes mellitus enrolled in 42 short-term, double-blind, randomized clinical studies with rosiglitazone,” 17 Pharmacoepidem. & Drug Safety 769, 770 (2008).

In its pooled analysis, GSK was clearly erring on the side of safety in creating its composite end point, but the crucial point is that GSK included events that had nothing to do with MI.  The MDL court appears to have accepted uncritically the plaintiffs’ expert witnesses’ claim that the difference between myocardial ischemic events and MI is only a matter of degree.  The Court found “that the experts were able to draw reliable conclusions about myocardial infarction” from a meta-analysis about a different end point, “by virtue of their expertise and the available data.”  Op. at 10.  This is hand waiving or medical alchemy.

Uncritical Acceptance of Mechanistic Evidence Related to Increased Congestive Heart Failure (CHF) in Avandia Users

The court noted that plaintiffs’ expert witnesses relied upon a well-established relationship  between Avandia and congestive heart failure (CHF).  Op. at 14.  True, true, but immaterial.  Avandia causes fluid retention, but so do other drugs in this class of drugs as well.  Actos causes fluid retention, and carries the same warning for CHF, but there is no evidence that Actos causes MI or stroke.  Although the Court’s desire to have a mechanism of causation is understandable, that desire cannot substitute for actual evidence.

Misuse of Power Analyses

The Avandia MDL Court mistakenly referred to inadequate statistical power in the context of interpreting data of heart attacks in Avandia RCTs. 

“If the sample size is too small to adequately assess whether the substance is associated with the outcome of interest, statisticians say that the study lacks the power necessary to test the hypothesis. Plaintiffs’ experts argue, among other points, that the RCTs upon which GSK relies are all underpowered to study cardiac risks.”

Op. at 5.

The Court might have helped itself by adverting to the Reference Manual of Scientific Evidence:

“Power is the chance that a statistical test will declare an effect when there is an effect to declare. This chance depends on the size of the effect and the size of the sample.”

Federal Judical Center, Reference Manual Scientific Evidence 2d ed. 125 – 26, 357 (2000) (internal citations omitted).  In other words, you cannot assess the power of the study unless you specify the size of the association of the alternative hypothesis, and the sample size, among other things.  It is true that most of the Avandia trials were not powered to detect heart attacks, but the concept of power requires the user to specify at least the alternative hypothesis against which the study is being assessed for power. Once the studies were completed, and the data became available, there was no longer any need or use for the consideration of power; the statistical precision of the studies’ results was given by their confidence intervals.

Incorrect Use of the Concept of Replication

The MDL court erred in accepting the plaintiffs’ expert witnesses’ bolstering of Nissen’s meta-analytic results by their claim that Nissen’s results had been “replicated”:

“[T]he NISSEN results have been replicated by other researchers. For example, the SINGH meta-analysis pooled data from four long-term clinical trials, and also found a statistically significant increase in the risk of myocardial infarction for patients taking Avandia. GSK and the FDA have also replicated the results of NISSEN through their own meta-analyses.”

Op. at 6 (internal citations omitted).

“The SINGH, GSK and FDA meta-analyses replicated the key findings of the NISSEN study.43″

Op. at 17.

These statements mistakenly suggest that Nissen’s meta-analysis was able to generate a reliable conclusion that there was a statistically significant association between Avandia use and MI.  The Court’s insistence that Nissesn was replicated does not become more true for having been stated twice.  Nissen’s meta-analysis was not an observational study in the usual sense.  His publication made very clear what studies were included (and not at all clear what studies were excluded), and the meta-analytic model that he used.  Thus, it is trivially true that anyone could have replicated his analysis, and indeed, several researchers did so.  See, e.g., George A. Diamond, MD, et al., “Uncertain Effects of Rosiglitazone on the Risk for Myocardial Infarction and Cardiovascular Death,” 147 Ann. Intern. Med. 578 (2007).

But Nissen’s results were not replicated by Singh, GSK, or the FDA, because these other meta-analyses used different methods, different endpoints (in GSK’s analysis), different inclusion criteria, different data, and different interpretative methods.  Most important, GSK and FDA could not reproduce the statistically significant finding for their summary estimate of association between Avandia and heart attacks.

One definition of replication that the MDL court might have consulted makes clear that replication is a repeat of the same experiment to determine whether the same (or a consistent) result is obtained:

“REPLICATION — The execution of an experiment or survey more than once so as to confirm the findings, increase precision, and obtain a closer estimation of sampling error.  Exact replication should be distinguished from consistency of results on replication.  Exact replication is often possible in the physical sciences, but in the biological and behavioral sciences, to which epidemiology belongs, consistency of results on replication is often the best that can be attained. Consistency of results on replication is perhaps the most important criterion in judgments of causality.”

Miquel Porta, Sander Greenland, and John M. Last, eds., A Dictionary of Epidemiology, 5th ed., at 214 (2008).  The meta-analyses of Singh, GSK, and FDA did not, and could not, replicate Nissen’s.  Singh’s meta-analysis obtained a result similar to Nissen’s, but the other meta-analyses by GSK, FDA, and Manucci failed to yield a statistically significant result for MI.  This is replication only in Wonderland.

It is hard to escape the conclusion that the MDL denied GSK intellectual due process of law.

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