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Prior Probability: the Dirty Little Secret of “Evidence-Based Alternative Medicine”—Continued Again

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…)

Posted in: Homeopathy, Medical Academia, Medical Ethics, Politics and Regulation, Science and Medicine

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Antiscience-Based Medicine in South Africa

South Africa’s Health Minister, Manto Tshabalala-Msimang, is fighting to protect the traditional healers of her country from having their methods tested scientifically. She warns that, “We cannot use Western models of protocols for research and development,” and that she does not want the incorporation of traditional healing to get “bogged down in clinical trials.” Her arguments are anti-scientific and represent a health tragedy for South Africa. However, such attitudes are not uncommon within the community of sectarian medicine and represent some of the common rhetoric used to disguise anti-scientific positions.

This is also not the first controversial statement made by South Africa’s health minister. In 2006 she advocated using garlic and beetroot to treat HIV infection, prompting outrage from South Africa’s academic community. In response to criticism about delays and funding cuts in providing anti-retroviral drugs to HIV sufferers in South Africa, the Health Minister said, “Garlic is absolutely critical, we need to do research on it. We cannot just ridicule it.” South Africa’s president, Thabo Mbeki, resisted calls for Ms. Tshabalala-Msimang’s resignation.

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Posted in: Politics and Regulation, Science and Medicine

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When the popularity of new surgical procedures outpaces science

ResearchBlogging.orgIn science- and evidence-based medicine, the evaluation of surgical procedures represents a unique challenge that is truly qualitatively different from the challenges in medical specialties. Perhaps the most daunting of these challenges is that it is often either ethically unacceptable or logistically impossible to do the gold-standard clinical trial, a double-blind, randomized placebo trial for an operation. After all, the “placebo” in a surgical trial involves patients to anaesthesia, making an incision or incisions like the ones used for the operation under study, and then not doing the operation. Clearly, even leaving the ethics aside, it’s impossible to blind the surgeons and operative team involved to which treatment, real surgery or placebo, the patient is receiving without having a different surgeon do the surgery from the one overseeing the postoperative care of the patient, with the operative surgeon barred from communicating to the postoperative surgeon what happened in the operating room and from participating in the postoperative care of the patient upon whom he operated. This sort of restriction, besides being also highly dubious ethically speaking, goes against the grain of surgical culture, in which a surgeon is expected to provide the postoperative care for his patients almost as a matter of surgical honor. A final problem that complicates any surgical trial is that surgeons of differing technical operating skill will necessarily be involved, and surgical skill is indeed very important in determining outcome. Although there have been examples of double-blinded trials with sham surgery as placebo, for example, in injecting dopamine-producing cells into the brain to treat Parkinson’s disease, difficulties doing such studies tend to force us as surgeons in many cases either to rely on retrospective data, prospective non-randomized data, or, when we’re lucky, a prospective randomized (but not double-blinded) trial of one surgical procedure versus another.
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Posted in: Clinical Trials, Medical Ethics, Science and Medicine, Surgical Procedures

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Prior Probability: the Dirty Little Secret of “Evidence-Based Alternative Medicine”—Continued

This is an addendum to my previous entry on Bayesian statistics for clinical research.† After that posting, a few comments made it clear that I needed to add some words about estimating prior probabilities of therapeutic hypotheses. This is a huge topic that I will discuss briefly. In that, happily, I am abetted by my own ignorance. Thus I apologize in advance for simplistic or incomplete explanations. Also, when I mention misconceptions about either Bayesian or “frequentist” statistics, I am not doing so with particular readers in mind, even if certain comments may have triggered my thinking. I am quite willing to give readers credit for more insight into these issues than might be apparent from my own comments, which reflect common, initial difficulties in digesting the differences between the two inferential approaches. Those include my own difficulties, after years of assuming that the “frequentist” approach was both comprehensive and rational—while I had only a cursory understanding of it. That, I imagine, placed me well within two standard deviations of the mean level of statistical knowledge held by physicians in general.

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

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Antibiotics for Sinusitis

You’re a patient. That cold just isn’t getting better and you have purulent drainage from your nose, and your face hurts and your teeth hurt. You probably have sinusitis, right? You go to a doctor to get an antibiotic.

You’re a doctor. Deep down, you know there’s a good chance the patient has a self-resolving condition.  You’d rather not do x-rays on every patient who presents with these symptoms, because x-rays are expensive, expose the patient to harmful radiation, and they are not always accurate.  You could puncture the sinuses and take a sample for bacteriological culture, but that’s expensive, painful, and the patient would NOT appreciate it. The patient may not really need treatment, but you want very much to do something to help. If you can find a reason to give the patient an antibiotic, you can feel that you have done something worthwhile.  Antibiotics don’t work for a viral infection, but you rationalize that you’re not 100% sure it’s not bacterial, and that sometimes a bacterial infection develops superimposed on a viral infection and mild bacterial infections can develop into severe ones with complications, and maybe you could ward that off.  You convince yourself that it really would be prudent to prescribe an antibiotic. Both you and your patient are happy. The patient gets better. You remember this pleasant experience and are reinforced to do the same next time.

Maybe that’s not such a good idea.

A recent study in JAMA showed that antibiotics were not superior to placebo for treating bacterial sinusitis diagnosed by the clinical criteria used by many primary care physicians. There is a growing concern that we have been overtreating sinus infections. Recent research has also shown that we were overtreating ear infections in children, that many of them resolve just as fast without treatment. That doesn’t mean antibiotics should never be used for ear infections. There are now guidelines for using age and clinical presentation to determine which children to treat and which ones can be safely observed without antibiotics. Most of these observed ear infections will resolve but some will eventually require antibiotics too. The situation with sinusitis is similar: most patients may not need antibiotics, and we’re trying to thrash out better criteria for identifying those who will.

Critics point to this kind of thing as a defect of conventional medicine. We use treatments that are not based on good evidence. We do things for years and then find out we were wrong. New studies are constantly contradicting older studies. We keep changing our minds. (more…)

Posted in: Science and Medicine

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Toxic myths about vaccines

Ever since there have been vaccines, there has been an antivaccination movement. It began shortly after Edward Jenner discovered how to use the weaker cowpox virus to induce long-lasting immunity to smallpox, there has been resistance to the concept of vaccination, a resistance that continues to this very day. Reasons for this resistance have ranged from religious, to fear of injecting foreign substances, to simple resistance to the government telling people what to do. Some fear even the infitessimally small risk that vaccines pose for the benefit of resistance to disease far more than they fear the diseases themselves, a result of the very success of modern vaccines. Of course, vaccines, like any other medical intervention, are not without risks, making it easy for them to jump on any hint of harm done by vaccines, whether real or imagined, even though vaccines are among the very safest of treatments.

One of the biggest myths that antivaccinationists believe and like to use to stoke the fear of vaccines is the concept that they are full of “toxins.” The myth that mercury in the thimerosal preservative commonly used in vaccines in the U.S. until early 2002 was a major cause of autism is simply the most recent bogeyman used to try to argue that vaccines do more harm than good, as was the scare campaign engineered in response to Andrew Wakefield’s poor science claiming a link between the MMR vaccine and autism. Now that study after study have failed to find or corroborate a link between thimerosal in vaccines or vaccines in general and autism to the point where even the most zealous of zealots are having a hard time defending the claim that mercury in vaccines cause autism any more, predictably the campaign against vaccines has fallen back on the old “toxins” myth. If you peruse antivaccinationist websites, it won’t take long to find articles claiming that vaccines are full of the most terrifying and nasty toxins. Examples in the media abound as well. For example, Jenny McCarthy, comic actress and former Playboy Playmate who has been doing the talk show and publicity circuit lately to plug her book in which she claims that vaccines caused her son’s autism and that she was able to cure it with “biomedical” interventions and diet, recently gave an interview in which she said:

What I really am is “anti-toxins” in the vaccines. I do believe that there is a correlation between vaccinations and autism. I don’t think it’s the sole cause, but I think they’re triggering–it’s triggering–autism in these kids. A really great example is…is, sometimes obesity can trigger diabetes. I do believe that vaccines can trigger autism…It’s so much more than just mercury. That is one ingredient in the recipe of autism…I’m talking about all of them. I’m calling for cleaning out the toxins. People don’t realize that there is aluminum, ether, antifreeze, still mercury, in the shots…People are afraid of secondhand smoke, but they’re OK with injecting the second worst neurotoxin on the planet in newborns.

Another example of what I sometimes call the “toxin gambit” comes from Deirdre Imus, wife of shock jock Don Imus, with both husband and wife being well-known and reliable media boosters of the claim that vaccines somehow cause autism:

So, where are the evidenced based (conflict free) studies that prove the safety of these “trace” amounts and proof that there are “no biological effects” of any amount of mercury being injected into our children and pregnant moms? Also, where are the evidence based studies proving the safety of vaccines given to pregnant moms and our children that contain other toxins such as aluminum and formaldehyde?

The most recent example of this tactic comes from an organization called Generation Rescue, which just last week ran a full-page ad in USA Today, paid for in part by Jenny McCarthy and her present boyfriend Jim Carrey:

antivaxgradvertisement.jpg

Besides being one of the most egregious examples of a post hoc ergo propter hoc fallacy that I’ve ever seen from an antivaccination site, this Generation Rescue ad demonstrates clearly a new strategy (or, more properly, a resurrection of an old technique) now that science is coming down conclusively against mercury in vaccines as a cause of autism, a strategy of propagating fear by linking vaccines with “toxins.” So what’s the real story? Are there really deadly toxins in vaccines that parents should be worried about?
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Posted in: Public Health, Science and Medicine, Science and the Media, Vaccines

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Prior Probability: The Dirty Little Secret of “Evidence-Based Alternative Medicine”

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.
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Posted in: Basic Science, Clinical Trials, Homeopathy, Science and Medicine

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Hype over science: Does acupuncture really improve the chances of success for in vitro fertilization?

There it was on Friday greeting me on the ABC News website: “Study: Acupuncture May Boost Pregnancy” in bold blue letters, with the title of the webpage being “Needles Help You Become Pregnant.” The story began:

It sounds far-fetched sticking needles in women to help them become pregnant but a scientific review suggests that acupuncture might improve the odds of conceiving if done right before or after embryos are placed in the womb.

The surprising finding is far from proven, and there are only theories for how and why acupuncture might work. However, some fertility specialists say they are hopeful that this relatively inexpensive and simple treatment might ultimately prove to be a useful add-on to traditional methods.

By the end of the day, the story was all over the media, including radio, TV, news websites, the blogosphere, and various other outlets, all trumpeting the message that a scientific study says that acupuncture can help infertile couples conceive. Nary a skeptical word seemed to be found. Knowing very well just how far parents will go to conceive, I was curious: Did this study actually say what the media says it said? What was so new and radical about this study that it rated a press release and a lot of promotion? Do we here at SBM (particularly Steve) need to rethink our extreme skepticism about acupuncture, given the poor quality evidence and lack of even a glimmer of a convincing physiologic mechanism to explain its supposed activities?
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Posted in: Acupuncture, Clinical Trials, Energy Medicine, Science and Medicine, Surgical Procedures

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Homeopathy and Evidence-Based Medicine: Back to the Future Part V

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.”

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

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The International Network of Cholesterol Skeptics

There is an organization that calls itself The International Network of Cholesterol Skeptics (THINCS). Its members “thinc” they are smarter than the average doctor. They “thinc” that cholesterol has nothing to do with cardiovascular disease and that we have been deluded into waging a “cholesterol campaign” for which the scientific evidence is non-existent. They say, “What we all oppose is that animal fat and high cholesterol play a role.” I find even the wording of this statement problematical: one does not usually hear scientists “opposing” matters of fact or non-fact. They go on to say, “The aim with this website is to inform our colleagues and the public that this idea is not supported by scientific evidence; in fact, for many years a huge number of scientific studies have directly contradicted it.”

They tell us about those contradicting studies; but they don’t tell us about the flaws in those studies, they misrepresent some of the results, and they don’t tell us about the many good studies that support the cholesterol/heart link. The issue is a complex one, and it is easy to find studies to support any claim. Good science is about weighing all the evidence pro and con before reaching a conclusion. As far as I can see, these folks have cherry-picked the literature to support an agenda. They seem to have a vendetta against statin drugs in particular.

The website solicits complaints of adverse effects from statin drugs. It features a petition to the WHO that you can sign requesting an investigation of statin side effects. It alleges that lowering cholesterol endangers the elderly. It provides “what the medical journals and newspapers won’t let you hear” – letters and papers that have been rejected for publication. It lists books, published papers and talks by its members. It solicits financial contributions to the cause.

This movement seems to have started with Uffe Ravnskov’s book The Cholesterol Myths, published in Swedish in 1991 and in English in 2000. That book has been severely criticized, for instance in The Skeptic’s Dictionary , where Bob Carroll points out some of the distortions and deceptive techniques found in the cholesterol skeptics’ arguments. A typical claim: “Cholesterol is highly protective against cancer, infection and atherosclerosis” and “high TC [total cholesterol] and LDL levels are beneficial at all ages.” These statements are not only false, they are potentially dangerous to the health of those who believe them. (more…)

Posted in: Pharmaceuticals, Science and Medicine

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