After the previous posting on the Bayesian approach to clinical trial data, several new comments made it clear to me that more needed to be said. This posting addresses those comments and adds a few more observations regarding the unfortunate consequences of EBM’s neglect of prior probability as it applies to “complementary and alternative medicine” (“CAM”).†
The “Galileo Gambit” and the Statistics Gambit
Reader durvit wrote:
A very interesting example, for a number of people, might be estimating the prior probability for Marshall and Warren’s early work on Helicobacter pylori and its impact on gastroduodenal management. I frequently have Marshall quoted to me as a variation on the Galileo gambit, so establishing whether he and Warren would have been helped or hindered by Bayesian techniques would be useful.
This suggestion raises a couple of issues. First, the “Galileo gambit” regarding Marshall and Warren’s discovery is a straw man (as durvit seems to have surmised). (more…)
This is actually the second entry in this series;† the first was Part V of the Homeopathy and Evidence-Based Medicine series, which began the discussion of why Evidence-Based Medicine (EBM) is not up to the task of evaluating highly implausible claims. That discussion made the point that EBM favors equivocal clinical trial data over basic science, even if the latter is both firmly established and refutes the clinical claim. It suggested that this failure in calculus is not an indictment of EBM’s originators, but rather was an understandable lapse on their part: it never occurred to them, even as recently as 1990, that EBM would soon be asked to judge contests pitting low powered, bias-prone clinical investigations and reviews against facts of nature elucidated by voluminous and rigorous experimentation. Thus although EBM correctly recognizes that basic science is an insufficient basis for determining the safety and effectiveness of a new medical treatment, it overlooks its necessary place in that exercise.
This entry develops the argument in a more formal way. In so doing it advocates a solution to the problem that has been offered by several others, but so far without real success: the adoption of Bayesian inference for evaluating clinical trial data.
Homeopathy and Science: Discussion, Summary and Conclusions
I was not surprised by a couple of the dissenting comments after Part IV of this blog. One writer worried that I had neglected, presumably for nefarious reasons, to cite replications of Benveniste’s results; another cited several examples of “positive” homeopathy studies that I had failed to mention. I answered some of those points here. I am fully aware of such “positive” reports, including those seeming to support Benveniste. I didn’t cite them, but not in some futile hope of concealing their existence from the watchful eyes of the readership. I also didn’t cite several “negative” reports, including an independent, disconfirming report of one of the claims of David Reilly, whose words began this series,* and the most recent of several reviews (referenced here) to conclude that “the clinical effects of homoeopathy are placebo effects.” I didn’t cite those reports for the same reasons that I didn’t cite the “positive” studies: they are mere footnotes to the overwhelming evidence against homeopathy.
To explain why, it will be necessary to discuss some of the strengths and weaknesses of the project known as “Evidence-Based Medicine.”
Homeopathy and Science
This week’s entry† is a summary of some of the tests of homeopathy. It is a necessary prelude to a discussion of how homeopaths and their apologists promote the method. Several tenets of homeopathy lend themselves to tests. The doctrine of similia similibus curantur (“like cures like”) was tested by Hahnemann himself, as introduced in Part I of this blog. It is a special case that will be discussed further below. Hahnemann’s second doctrine, “infinitesimals,” suggests laboratory, animal, and clinical studies looking for specific effects of homeopathic preparations.
“Provings,” also called “homeopathic pathogenic trials,” suggest testing “provers” for the ability to distinguish between homeopathic preparations and placebos, and suggest asking homeopaths to identify specific remedies solely by the “symptoms” they elicit in “provers.” The homeopathic interview and prescribing scheme, gathering copious “symptoms” and matching them to the appropriate “remedy” in the Materia Medica, suggests testing homeopaths for consistency in symptom interpretations and prescriptions. The clinical practice suggests outcome studies, both of individual “conditions” (with the caveat that, strictly speaking, homeopathy does not recognize disease categories—only “symptom” complexes) and of the practice as a whole.
Several of these categories overlap. Several have been tested: the results have overwhelmingly failed to confirm homeopathy’s claims. I will mention a few of the more conspicuous examples.
Part II of this blog† introduced the homeopathic understanding of “symptoms” as they pertain both to “provings” in healthy subjects (now called “homeopathic pathogenic trials” or “HPTs”) and to histories elicited from patients. Hahnemann conflated “symptoms” and every random itch, ache, pain, sniffle, feeling, thought, dream, pimple or other sign, and anything else that might occur to a subject or a patient. This was amply demonstrated by Oliver Wendell Holmes, Sr., who seemed to doubt that such a morass would yield useful information. As unlikely as it may seem, today’s homeopaths are every bit as whimsical in their elicitation of “symptoms” as was Hahnemann.
Part I of this blog† summarized the origin of homeopathy, invented in 1790 by Samuel Christian Hahnemann. It discussed Hahnemann’s first two “homœopathic laws of nature,” similia similibus curantur (like cures like) and the “law of infinitesimals,” and showed that his rationales for each have long been refuted. Hahnemann proclaimed a third doctrine, the “law of psora” ["itch"], said by him to be “the mother of all true chronic diseases except the syphilitic and sycotic.” Oddly, it seems to have been forgotten.
Part II gives Hahnemann the opportunity to explain his assertions more thoroughly, as is his due. It considers those assertions from the vantage point of modernity, as is ours.
“Leave None of them Uncured”
According to Hahnemann, homeopathy is a panacea:
“Now, however, in all careful trials, pure experience, the sole and infallible oracle of the healing art, teaches us that actually that medicine which, in its action on the healthy human body, has demonstrated its power of producing the greatest number of symptoms similar to those observable in the case of disease under treatment, does also, in doses of suitable potency and attenuation, rapidly, radically and permanently remove the totality of the symptoms of this morbid state, that is to say, the whole disease present, and change it into health; and that all medicines cure, without exception, those diseases whose symptoms most nearly resemble their own, and leave none of them uncured.”
How might this happen?
“Either homeopathy works or controlled trials don’t!”
—Scottish homeopath David Reilly at the 2001 Harvard Medical School Complementary and Integrative Medicine Conference.
Reilly based that assertion on his own series of four small studies of homeopathic treatments of hay fever, asthma, and allergic rhinitis, the outcomes of which had been inconsistent and largely subjective. (1) Later he explained that small-minded skeptics in “conventional medicine” assume “homeopathy doesn’t work because it can’t work,” a view echoed by conference host Dr. David Eisenberg, then the Director of the Center for Alternative Medicine Research and Education at Harvard Medical School (now of the Osher Center); these comments were met with appreciative laughter from the partisan audience. If such charges were valid, it would indeed be fortunate that Harvard Medical School, several other medical schools, and the National Center for Complementary and Alternative Medicine (NCCAM) are promoting homeopathy, both as a clinical method and as a topic worthy of research.