The SkepDoc: Evidence-Based Medicine, Tooth Fairy Science, and Cinderella Medicine
Hall, Harriet, Skeptic (Altadena, CA)
THE TERM EVIDENCE-BASED MEDICINE (EBM) first appeared in the medical literature in 1992. There were two previous EBMs: Expert-Based Medicine and Experience-Based Medicine. In the 4th century BCE, Aristotle said men have more teeth than women. He was the expert, and for many centuries his error was perpetuated because no one dared question his authority and no one bothered to look in mouths and count teeth.
Then we relied on experience. When I was in medical school, professors would often say something to the effect, "In my experience, drug A is the best treatment for disease B." Dr. Mark Crislip says the three most dangerous words in medicine are "in my experience" because experience is so compelling and so often wrong. Richard Feynman said, "The first principle is that you must not fool yoursetf--and you are the easiest person to fool:'
Why Evidence Based Medicine is Essential
Experience is deceptive. When a patient gets better with a treatment, it could be because of the treatment but it could also be due to:
* Improvement of symptoms because of the natural course of the disease.
* Regression to the mean (an exceptionally high blood pressure reading will naturally be followed by a lower one closer to the average BP).
* Spontaneous remission.
* Inaccurate observation of what really happened.
* Biases that influence our interpretation of events.
* Unidentified co-interventions.
* Reinforced expectations.
* Classical (Pavlovian) conditioning.
* Social learning.
* Many other psychosocial and psychobiological factors.
Even the most reasonable-sounding, intuitively obvious beliefs may be wrong. The gold standard of EBM is the randomized controlled trial (RCT) where the treatment is compared to a placebo with all other factors being equal.
EBM is a great concept, but its implementation has been flawed. It gives short shrift to plausibility and appears to worship the RCT above all else. If an RCT showed that scratching your nose cured cancer, EBM would accept it, even while a skeptical thinker would assume something was wrong with the study.
How much of current practice is evidence-based? 78% of our interventions are based on some form of compelling evidence, and 38% are supported by RCTs. More evidence is always better, but it's unreasonable to hope for everything we do to be supported by RCTs. The British Medical Journal published a delightfully tongue-in-cheek proposal ridiculing those who are overly attached to RCTs:
The effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.
We don't need to do an RCT pushing people out of planes with and without parachutes to know what would happen. As the old adage says, "You don't need a parachute to skydive; you only need a parachute to skydive twice." We don't need to do an RCT of surgery for appendicitis, of setting broken bones, or of controlling blood loss in trauma and surgery. If we have a life-saving treatment, we can't ethically deny it to half of our subjects for a control group.
Homeopathy says that you can dilute out all the molecules of the original substance and the water will remember it and have effects opposite to those of the original substance. Based on the sort of basic science evidence that amounts to "established knowledge," we can confidently say that homeopathy can't possibly work as claimed. Is it realistic to assume that a huge body of established knowledge could be overthrown by a few ambiguous clinical trials? …