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Archive for March, 2011

Of SBM and EBM Redux. Part IV, Continued: More Cochrane and a little Bayes

OK, I admit that I pulled a fast one. I never finished the last post as promised, so here it is.

Cochrane Continued

In the last post I alluded to the 2006 Cochrane Laetrile review, the conclusion of which was:

This systematic review has clearly identified the need for randomised or controlled clinical trials assessing the effectiveness of Laetrile or amygdalin for cancer treatment.

I’d previously asserted that this conclusion “stand[s] the rationale for RCTs on its head,” because a rigorous, disconfirming case series had long ago put the matter to rest. Later I reported that Edzard Ernst, one of the Cochrane authors, had changed his mind, writing, “Would I argue for more Laetrile studies? NO.” That in itself is a reason for optimism, but Dr. Ernst is such an exception among “CAM” researchers that it almost seemed not to count.

Until recently, however, I’d only seen the abstract of the Cochrane Laetrile review. Now I’ve read the entire review, and there’s a very pleasant surprise in it (Professor Simon, take notice). In a section labeled “Feedback” is this letter from another Cochrane reviewer, which was apparently added in August of 2006, well before I voiced my own objections:

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Posted in: Clinical Trials, Homeopathy, Medical Academia, Science and Medicine

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Topical NSAIDs

I have a mental basket of drugs that I suspect may be placebos. In that basket were the topical versions of non-steroidal anti-inflammatory drugs (NSAIDs). When the first products were commercially marketed over a decade ago, I found the clinical evidence unconvincing, and I suspected that the modestly positive effects were probably due to simply rubbing the affected area, or possibly due to the effects of the cream or vehicle itself. Frankly, I didn’t think these products worked. So when I recently noticed a topical NSAID appear for sale as an over-the-counter treatment for muscle aches and pains (seemingly only in Canada, for now), I was confident it would make a good case study in bad science.

It’s not that I’m partial to the oral NSAIDs. Yes, they’re among the most versatile, and probably most well-loved drugs in our modern medicine cabinet. They offer good pain control, reduce inflammation and can eliminate fever. We start using it in our sick and feverish infants, through childhood and adulthood for the aches and pains of modern life, and into our later years for the treatment of degenerative disease like osteoarthritis, which affects pretty much everyone as we age. An astonishing 17 million Americans use NSAIDs on a daily basis, and this number is expected to grow as the population ages. In the running groups I frequent, ibuprofen has the affectionate nickname “Vitamin I”, where it’s perceived as an essential ingredient for dealing with the consequences of training.

But NSAIDs have a long list of side effects. Not only do they cause stomach ulcers and bleeding by damaging the gastrointestinal mucosa, there are heart risks, too. It was the arrival (and departure) of the drugs Bextra and Vioxx that led to documentation of the potential for cardiovascular toxicity. And now there’s data to suggest that these effects are not limited to the “COX-2″ drugs – almost all NSAIDs, including the old standbys we have used for years, seem capable of raising the risks of heart attacks and strokes.

So despite my initial skepticism, I took another look at the topical NSAIDs. The data were not what I expected.

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Posted in: Pharmaceuticals, Science and Medicine

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Placebo Effect for Pain

It has long been recognized that there are substantial multifactorial placebo effects that create real and illusory improvements in response to even an inactive treatment. There is a tendency, however (especially in popular discussion), to oversimplify placebo effects – to treat them as one mind-over-matter effect for all outcomes. Meanwhile researchers are elucidating the many mechanisms that go into measured placebo effects, and the differing magnitude of placebo effects for different outcomes.

For example, placebo effects for pain appear to be maximal, while placebo effects for outcomes like cancer survival appear to be minimal.

A recent study sheds additional light on the expectation placebo effect for pain. The effect is, not surprisingly, substantial. However it does not extrapolate to placebo effects for outcomes other than pain, and the results of this very study give some indication why. From the abstract:

The effect of a fixed concentration of the μ-opioid agonist remifentanil on constant heat pain was assessed under three experimental conditions using a within-subject design: with no expectation of analgesia, with expectancy of a positive analgesic effect, and with negative expectancy of analgesia (that is, expectation of hyperalgesia or exacerbation of pain).

What they found was that the positive expectation group reported twice the analgesic effect as the no expectation group, and the negative expectation group reported no analgesic effect. This is a dramatic effect, but not surprising.

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Posted in: Neuroscience/Mental Health, Pharmaceuticals

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Questioning the Annual Pelvic Exam

A new article in the Journal of Women’s Health by Westhoff, Jones, and Guiahi asks “Do New Guidelines and Technology Make the Routine Pelvic Examination Obsolete?”

The pelvic exam consists of two main components: the insertion of a speculum to visualize the cervix and the bimanual exam where the practitioner inserts two fingers into the vagina and puts the other hand on the abdomen to palpate the uterus and ovaries. The rationales for a pelvic exam in asymptomatic women boil down to these:

  • Screening for Chlamydia and gonorrhea
  • Evaluation before prescribing hormonal contraceptives
  • Screening for cervical cancer
  • Early detection of ovarian cancer

None of these are supported by the evidence. Eliminating bimanual exams and limiting speculum exams in asymptomatic patients would reduce costs without reducing health benefits, allowing for better use of resources for services of proven benefit. Pelvic exams are necessary only for symptomatic patients and for follow-up of known abnormalities. (more…)

Posted in: Obstetrics & gynecology

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