Science-Based Medicine

One of the recurring topics here at SBM is the idea of the placebo: What it is, what it isn’t, and how it complicates our evaluation of the scientific evidence. One my earliest lessons after I started following this blog (I was a reader long before I was a writer) was that I didn’t understand placebos well enough to even describe them correctly. Importantly, there is no single “placebo effect”. They are “placebo effects”, a range of variables that can include natural variation in the condition being studied, psychological factors and subjective effects reported by patients, as well as observer bias by researchers studying a condition. All of these, when evaluated in clinical trials, produce non-specific background noise that needs to be removed from the analysis. Consequently, we compare between the active treatment and the placebo to determine if there are an incremental benefits, to which we apply statistical tests to determine the likelihood that the differences between the intervention and the placebo groups are real. Removed from the observational nature of the clinical trial, we can’t expect the observed “placebo effects” to persist, as they’re partially a consequence of the trial itself. A more detailed review of placebos is a post in and of itself, so I’ll refer you to resources that describe why placebo effects are plural, that placebo effects are subjective rather than objective and there is no persuasive evidence to suggest that placebo effects offer any health benefits. What’s most important is the understanding that placebo effects are a measurement artifact, not a therapeutic effect.

Placebo effects are regular topics within in SBM posts because an understanding of placebo effects is essential to evaluating the evidence supporting (so-called) complementary and alternative medicine, or CAM. As better quality research increasingly confirms that the effects from CAM are largely, if not completely, attributable to placebo effects, we’ve seen the promoters of CAM shifting tactics. No longer able to honestly claim that CAM has therapeutic effects, “treatments” such as acupuncture or homeopathy are increasingly promoted as strategies that”harness the power of placebo” without all the pesky costs or side effects of real medical interventions. But this is simply special pleading from purveyors and promoters. Unable to wish away the well-conducted trials that show them to be indistinguishable from placebos, they instead are spinning placebo effects as meaningful and worthy of pursuit – ideally with your favourite CAM therapy. Again, I’ll refer you to posts by David Gorski and Steven Novella who offer a more detailed description of how negative results can be spun to look positive. Because CAM’s effects are indistinguishable from placebo, we should not invest time and resources into pursuing them – we should instead focus on finding treatments that are demonstrably superior to placebo.

But what if physicians are already using placebos widely in practice? Setting aside the ethical issues for now, widespread placebo usage might suggest that physicians believe that placebos are effective treatments. And that’s the impression you may have had if you skimmed the medical headlines last week:

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Defenders of science-based medicine are often confronted with the question (challenged, really): what would it take to convince you that “my sacred cow treatment” works? The challenge contains a thinly veiled accusation — no amount of evidence would convince you because you are a nasty skeptic.

There is a threshold of evidence that would convince me of just about anything, however. In fact, I have been convinced that many scientific claims are likely to be true — sufficiently convinced to act upon the conclusion that they are true. In medicine this means that I am convinced enough to use them as a basis for medical practice.

There are many functional differences between practitioners of SBM and those who accept claims and practices that we would consider to be pseudoscience or fraud, but I was recently struck by one particular such difference — where we set the threshold of evidence before accepting a claim.

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In part I of this series I discussed clinical pathways – how clinicians approach problems and the role of diagnosis in this approach. In part II I discussed the thought processes involved in deciding which diagnostic tests are worth ordering.

In this post I will discuss some of the logical fallacies and heuristics that tend to bias and distort clinical reasoning. Many of these cognitive pitfalls apply to patients as well as clinicians.

Pattern Recognition and Data Mining

Science, including the particular manifestation we like to call science-based medicine, is about using objective methods to determine which patterns in the world are really real, vs. those that just seem to be real. The dire need for scientific methodology partly results from the fact that humans have an overwhelming tendency to automatically sift through large amounts of data looking for patterns, and we are very good at detecting patterns, even those that are just random fluctuations in that data.

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This is the second in a brief series of posts about how clinicians think. My purpose here is to elucidate how skeptical principles apply to clinical decision-making, but also as background to provide context to many of the articles we publish here.  In this installment I will review the factors that clinicians consider when deciding what tests to order for screening and when conducting a diagnostic workup.

The Gunshot Approach

Last week I discussed the “Dr. House” approach to medicine, using that particular TV character as an example of how medicine is often portrayed in fiction. Another aspect of the Dr. House image that is very misleading is his approach to diagnosis, which tends to be very linear. He decides what the most likely diagnosis is, then proceeds to either treat that entity or order a confirmatory diagnostic test. When that diagnosis fails, he then proceeds onto diagnosis B. A string of such failures then culminates in a flash of brilliance that allows him to make the actual obscure diagnosis and cure the patient. This approach is optimized for storytelling and drama, but is not how actual clinicians operate.

At the other end of the spectrum is what doctors often refer to as “the gunshot approach” – test for everything in hopes that you hit something. Another derogatory term that doctors throw around is “a fishing expedition,” referring to a diagnostic approach that amounts to hunting around for any possible diagnosis without having a real justification.

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You need to keep an open mind.

A common suggestion offered to naysayers of nonsense.

The usual retort concerns not letting one’s brain fall out.

Evaluating SCAM’s is less about having an open mind and more about having standards, a conceptual framework that is used to interpret and analyze new information. One of the benefits of writing and reading topics covered by science-based medicine (SBM) is it has clarified and sharpened the ideas by which I understand the world. Those concepts were nicely summed up by Steve Novella at Neurologica, and I reproduce them here, slightly modified. They should be on stone tablets, not quite commandants, but strong suggestions. The 8 strong suggestions somehow doesn’t cut it however. Continue Reading »

I practice in a university clinic which functions partly as a tertiary referral center, which means we get referrals from other specialists. I also get many referrals for second opinions. Sometimes the entire cause for the patient’s desire for a second opinion, it seems to me, is the simple fact that they did not understand the reasoning of the previous specialist. They were given a diagnosis and a course of treatment, but not an explanation of how their doctor arrived at those conclusions.

I am not being judgmental – different practices are under different pressures and time constraints, and it can be very difficult to gauge a patient’s understanding. Often the physician and the patient are proceeding based upon differing assumptions and narratives that are not expressly stated. The doctor may think they have explained the situation entirely, but simply did not confront misleading assumptions they were not aware their patient had.

This is part of the advantage of engaging the public about health issues and confronting pseudoscience, myths, and misconceptions – you develop a deep awareness of how the general public thinks about medicine.

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by Kenneth R. Foster & Lorne Trottier

Science-based medicine is great, but it all depends on how you evaluate the scientific evidence. A bad example is the  BioInitiative Report (BIR), an egregiously slanted review of health and biological effects of electromagnetic fields (EMF) of the sort that are produced by power lines, cellular telephones, Wi-Fi, and other mainstays of modern life. When first released in 2007, the BIR quickly became a key document used by anti-EMF activists in their various campaigns. Early in January 2013, the BIR appeared in a major update, to extensive media coverage.

The BIR concerns possible biological effects and health hazards of electromagnetic fields in two very different frequency ranges: at extremely low frequencies ELF’s of the sort emitted by power lines and appliances, and at radiofrequencies (RFs) of the sort that are transmitted by mobile phones, Wi-Fi and a host of other technologies. Both ELF and RF fields (which are subsumed under the more general EMF) are part of the electromagnetic spectrum, which includes infrared energy, light, ultraviolet energy, as well as X-rays.

ELF and RF fields are nonionizing, in that the energy of their photons is far too low to break chemical bonds, an effect that makes ionizing radiation such as X-rays so hazardous. Fields from power lines are at 50 or 60 Hz or cycles per second; those from mobile phones and other RF communications and broadcasting systems are in the range of hundreds or thousands of MHz (megahertz or million cycles per second). Simple physics tell us that a photon of 1GHz frequency has an energy of 6 millionths of an electron volt (eV), while the average thermal energy of a molecule is 0.03 eV and the ionization energy of a chemical bond is on the order of 1 eV

There are, of course, well-established hazards from excessive exposures to ELF and RF fields, which are mainly associated with electric shock (ELF) and excessive heating of tissue (RF). Such problems, however, require exposure to fields at vastly higher levels than anything that would be encountered in ordinary life. Most countries around the world have adopted roughly similar exposure limits that are designed to protect against these known hazards.

The possibility that the electromagnetic fields at much lower exposure levels can be bad for you has been a matter of public concern for many years. Countless public, scientific, and legal battles have been waged about possible health hazards produced by fields from power lines, cellular base stations, broadcasting facilities, and other technologies, despite the fact that public exposures from such technologies are invariably far below government exposure limits.
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If you’re a regular reader of this blog, I’ll bet you’re not a regular consumer of vitamins or supplements. I’m in that group. Aside from sporadic vitamin D in winter, I don’t take any vitamins or supplements routinely, nor do I give any to my children. Your reasons may be close to mine: There is little to no evidence suggesting that dietary deficiencies are widespread, nor is there good evidence to suggest that vitamin supplements are beneficial in the absence of deficiency. I don’t have any need for an other supplements, nor am I confident in the scientific evidence for many of them.This position of “no supplements” is a cautious and conservative one, but is based on a consideration of the scientific evidence. I view decisions about healthcare as evaluations of risk and benefit, and then cost if necessary. Given supplementation (with some exceptions) has no demonstrable benefits and, in some cases, a little risk, the odds favour not supplementing in most cases. Add in costs, and it’s even less attractive as a routine health strategy.

Yet a decision not to take vitamins or supplements regularly is becoming a minority position. Supplement use has grown over the past 40 years among Americans, with the National Health and Nutrition Examination Survey (NHANES) showing steadily increasing utilization among younger and older adults:
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A recent study published in the Proceedings of the National Academy of Sciences calls into question the standard mouse model of sepsis, trauma, and infection. The research is an excellent example of how proper science investigates its own methods.

Mouse and other animal models are essential to biomedical research. The goal is to find a specific animal model of a human disease and then conduct preliminary research on the animal model in order to determine which research is promising enough to study in humans. There are also non-animal assays and “test tube” type research that is used to screen potential treatments, but scientists still prefer a good animal model.

It is also understood that animal models are imperfect – mice are not humans, after all. Animal research is therefore not a substitute for human research. I and other SBM authors have regularly criticized proponents of dubious treatments who make clinical claims based upon preliminary animal research. Until something is studied in humans, we cannot make any reliable claims about its safety and efficacy in people.

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My son has been coughing for several weeks, and the cough will probably persist for another 2 or 3 weeks. Coughs last a long time. Patients think a cough will go away in less than a week but in reality they are likely to last several weeks.

Coughs are a pain for the patient and an annoyance for the people around them. You never really know if the cougher in the row behind you has asthma,  a post infectious cough or  is actively spewing TB or influenza all over the airplane.  I learned from Clinton the importance of not inhaling, especially on airplanes.

I tend to leave most symptoms alone if the they are not life threatening or otherwise unbearable for the patient. Codeine is the only really good cough suppressant and none of the over the counter cough medications are effective.  I assume that coughing with infection, like diarrhea, is beneficial. Key to treating all infections is to physically remove it. Undrained pus doesn’t heal, and a good cough is the most efficient way I know to remove potential pathogens from the lungs.

If there are benefits to suppressing the cough associated with acute respiratory infections I can’t find any and we have all seen people who, because of inability to cough secondary to rib fractures, develop severe pneumonia.  As a resident I had an elderly male die of just such a series of unfortunate events.

I suffer from a mild form the the naturalistic fallacy. I tend to let normal physiologic processes run their course unimpeded as long as they pose no harm to the patient.  So I do not treat infectious coughs, in part because medications are not effective, in part there is no benefit  and in part because the medications that are effective, and those that are not, have side effects.  Continue Reading »