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Of the Trial to Assess Chelation Therapy, Bayes, the NIH, and Human Studies Ethics

An experiment is ethical or not at its inception; it does not become ethical post hoc—ends do not justify means.
~ Henry K. Beecher

tact

A couple of weeks ago, Dr. Josephine Briggs, the Director of the National Center for Complementary and Alternative Medicine (NCCAM), posted a short essay on the NCCAM Research Blog touting the results of the Trial to Assess Chelation Therapy (TACT) (italics added):

The authors found that those receiving the active treatment clearly fared better than those receiving placebo. The accompanying editorial in the AHJ reminds readers about the value of equipoise and the need to “test our beliefs against evidence.”

Most physicians did not expect benefit from chelation treatment for cardiovascular disease. I readily admit, initially, I also did not expect we would find evidence that these treatments reduce heart attack, strokes, or death. So, the evidence of benefit coming from analyses of the TACT trial has been a surprise to many of us. The subgroup analyses are suggesting sizable benefit for diabetic patients—and also, importantly, no benefit for the non-diabetic patient. Clearly subgroup analyses, even if prespecified, do not give us the final answer. But it is also clear that more research is needed to test these important findings.

And TACT findings are indeed a reminder of the importance of retaining equipoise [sic], seeking further research aimed at replicating the findings, and neither accepting nor rejecting findings based on personal biases. The scientific process is designed to weed out our preconceived notions and replace them with evidence.

Dr. Briggs concluded:

So, TACT is a reminder—an open mind is at the center of the scientific method.

Dr. Briggs’s title was “Bayes’ Rule and Being Ready To Change Our Minds”, a reference to a recent editorial that had accompanied one of the TACT papers. That editorial, by Dr. Sanjay Kaul, a physician and statistician from UCLA, begins with this quotation:

Preconceived notions are the locks on the door to wisdom.
~ Merry Browne

Here is the relevant passage from Dr. Kaul’s editorial (italics added):

Sixth, it has been argued that the trial was unethical because there was no compelling clinical or preclinical evidence that chelation therapy has significant efficacy against atherosclerotic cardiovascular disease, and given that chelation therapy can cause harm, the risk was not minimal. A Bayesian analysis would not look kindly on the results because of the low prior probability of treatment effect (the so-called implausibility argument).6 This is an uncharitable (and unwarranted) interpretation of the data because previous systematic reviews concluded, “insufficient evidence to decide on the effectiveness or ineffectiveness of chelation therapy in improving clinical outcomes among people with atherosclerotic cardiovascular disease.” It is axiomatic that absence of evidence of efficacy is not the same as evidence of the absence of efficacy.

From a Bayesian perspective, the strength of evidence is often summarized using a Bayes factor, which is a measure of how well 2 competing hypotheses (the null and the alternate) predict the data. The Bayes factor and the corresponding strength of evidence for the primary end point result in TACT overall, and diabetic cohorts are shown in Table 1. The p-value of 0.035 for TACT overall cohort translates into a Bayes factor of 0.108, which means the evidence supports the null hypothesis ≈1/9th as strongly as it does the alternative. This reduces the null probability from 50% pretrial (justified by suspension of one’s belief in treatment effect) to 10% post-trial. Although this does not represent strong evidence against the null, it does reduce the level of skepticism surrounding chelation therapy. In the diabetic cohort, the nominal p-value of 0.0002 translates into a Bayes factor of 0.002 (1/500), which reduces the extremely skeptical prior null probability of 95% to 4% post- trial, indicating very strong evidence against the null.

In concluding, Dr. Kaul states:

Finally, TACT highlights the double standard when it comes to accepting inconvenient results not aligned with our preconceived notions on so-called dubious quack cures such as chelation…

Closed minds?

Dr. Kaul’s reference “6” above is to a lengthy article that we published in 2008 titled “Why the NIH Trial to Assess Chelation Therapy Should Be Abandoned”. So, it seems, both Drs. Briggs and Kaul were chastising us for our biased, preconceived beliefs about so-called dubious quack cures. Our minds were, apparently, not open. Let’s examine this contention. (more…)

Posted in: Clinical Trials, Health Fraud, Medical Academia, Medical Ethics, Politics and Regulation

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Dummy Medicine, Dummy Doctors, and a Dummy Degree, Part 2.0: Harvard Medical School and the Curious Case of Ted Kaptchuk, OMD

Review

The recent albuterol vs. placebo trial reported in the New England Journal of Medicine (NEJM) found that experimental subjects with asthma experienced substantial, measured improvements in lung function after inhaling albuterol, but not after inhaling placebo, undergoing sham acupuncture, or “no treatment.” It also found that the same subjects reported having felt substantially improved after either albuterol or each of the two sham treatments, but not after “no treatment.” Anthropologist Daniel Moerman, in an accompanying editorial, wrote, “the authors conclude that the patient reports were ‘unreliable,’ since they reported improvement when there was none”—precisely as any rational clinician or biomedical scientist would have concluded.

In Part 1 of this blog we saw that Moerman took issue with that conclusion. He argued, with just a bit of hedging, that the subjects’ perceptions of improvement were more important than objective measures of their lung function. I wondered how the NEJM editors had chosen someone whose bibliography predicted such an anti-medical opinion. I doubted that Editor-in-Chief Jeffrey Drazen, an expert in the pathophysiology of asthma, had ever heard of Moerman. I suggested, in a way that probably appeared facetious, that Ted Kaptchuk, the senior author of the asthma report, might have recommended him. (more…)

Posted in: Acupuncture, Chiropractic, Clinical Trials, Health Fraud, Herbs & Supplements, History, Medical Academia, Medical Ethics, Naturopathy, Pharmaceuticals, Science and Medicine, Science and the Media

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Wyeth vs. Levine: Should Drug Label Standards Be Determined By Juries?

It is with some degree of trepidation that I enter the fray on the Wyeth vs. Levine case. I’ve been watching the media frenzy about the lawsuit with interest – mostly because (for the first time in a while) I think that the pharmaceutical company is in the right on this one – and that most journalists (and even medical journal editors) have missed the salient points.

I think that a close review of the case is instructive in two ways. It shows: 1) the dangers of making legal decisions based on the perspective of the victim (a risk of harm equal to 1 in 20 million is unacceptable to that one person who suffered the consequence, but tolerable to the other 19,999,999 others) and 2) that a simple case of medical malpractice has made it all the way to the US Supreme Court because (as I discussed in my last post) a democratization of knowledge (juries reading a drug label) was believed to democratize expertise (how a physician would understand the label).
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Posted in: Pharmaceuticals, Politics and Regulation, Public Health

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