Nov 19 2007

How Much Modern Medicine is Evidence-Based

In response to my Homeopathy entry last week, reader Jasonb left the following comment:

I think debunking homeopathy is important and worthwhile. There is, however, a more pressing matter at hand.

Following on the heels of recent news that many drugs prescribed by doctors (and sold by pharmacies) lack an FDA approval, how many people are aware that LESS THAN FIFTY PERCENT (50%) of western medical practice is based on valid scientific evidence and some experts estimate that number is low as FIFTEEN PERCENT (15%).


At 15%, I have to imagine the whole of Alternative Medicine has more valid science behind it than that.

It would be a tremendous service if you could identify the top dozen or so western practices that would utterly astonish people to know have as much scientific validity as homeopathy. There has to be some real doozies at the top of the list.

Thanks for the comment, Jason, but I am afraid that the less than 50%, and as low as 15%, figures are myths, propagated by the critics of scientific medicine and advocates of “alternatives.” Like so many ideologically useful myths, the figures are now embedded in the culture, and it seems we will be hearing them over and over again.

Like most rumors and myths the “source” that people cite as support always turns out to be a secondary source – someone just spreading the rumor. It is nothing more than a “friend of a friend” story, where you can never get to the original friend that was the source of the information. Critics of mainstream medicine happily repeated the figure without ever verifying it. I will also note that the Washington Monthly article that was cited is a highly political piece, and while there are kernels of truth within it, it is also a highly distorted and agenda driven view of the current situation.

Fortunately, Bob Imrie (a skeptical veterinarian and great guy who sadly recently passed away) did the leg work of tracking down the original source. The 15% figure comes from a small survey of primary practice offices in the north of England conducted in 1961 – that’s right, almost half a century ago. Further, the survery was never intended to assess the degree to witch primary practices were evidence-based, but rather was looking at whether treatments were “specific” from the point of view of insurance reimbursement. So the 15% figure is misrepresented and half a century out of date.

What are the real figures? Well, there is some subjectivity to this because evidence-based is not black or white; there are degrees of evidence. Also, modern medicine has picked all the low hanging fruit, meaning that obvious treatments have been developed for straightforward situation. Bob Imrie gives the example of blood transfusions. If someone is bleeding to death, we stop the bleeding and transfuse blood to stabilize blood pressure. This is such a no-brainer that it would be unethical to conduct an experiment in which we let people continue to bleed and/or not transfuse them just to prove that doing so is a good idea.

But putting the obvious stuff aside, there are many institutions that expend a great deal of time and effort assessing the evidence-basis for what doctors do. Prominent among them are groups dedicated to evidence-based medicine – the purpose of which is to systematically review the evidence for specific practices. Estimates vary among the various fields of medicine – some specialties lend themselves to placebo-controlled trials more than others. But Imrie summarizes the evidence thusly:

Thus, published results show an average of 37.02% of interventions are supported by RCT (median = 38%). They show an average of 76% of interventions are supported by some form of compelling evidence (median = 78%).

Three quarters is a completely different world than “as low as 15%.” Also, we must consider that the other 25% is based on some evidence, even if not compelling, and typically will have a high degree of plausibility. You also have to take into consideration the context of treatment. If there is no evidence-based treatment available for a patient (or what is available has failed or cannot be used) then it is reasonable to try plausible if unproven therapies.

My personal experience is that nearly 100% of the clinical decisions I make are based upon the best available evidence combined with plausible and rational extension of what is known. I can’t think of any time when I use treatments that are based upon nothing, or even nothing but anecdote. At the very least there is a biologically plausible mechanism of action and adequate evidence for lack of harm. The only exception to this, of course, is experimental treatments – but they are highly regulated and follow their own stringent ethical guidelines.

Regarding “off-label” use of pharmaceuticals, this is also highly misleading. The FDA requires a high threshold of evidence for safety and effectiveness for a specific indication, and then only allow the company to market the drug for the specific indication. But the reality of medicine is very different. Diseases processes and diagnoses are not neat separate entities. The FDA process pretends that they are – it’s a fiction of convenience and everyone understands this.

For example, the FDA has approved the drug Cymbalta for painful diabetic neuropathy – a specific disease diagnosis. But diabetes can cause different kinds of nerve damage and different kinds of neuropathic pain. Neuropathic pain can also be caused by many different things. The neuropathic pain caused by diabetes may be similar or even identical to the neuropathic pain caused by trigeminal neuralgia or post-herpetic neuralgia. There is no reason to think that Cymbalta would not work for these other forms of neuropathic pain, but these would be off label uses.

The bottom line is that you should not equate off label with not based upon evidence. In many cases there is compelling evidence for off-label use, but it is not worth the company’s money to get an additional indication from the FDA. Company’s rarely do this – they only do it when they think it will increase the market for their drug. Scientists, however, will study approved drugs to see what the extent of their use truly is.

What about so-called alternative medicine? Despite Jason’s hunch, it is based upon almost no evidence at all. Modalities are alternative for a reason, because they are highly improbable and lack compelling evidence. Otherwise they would be mainstream, not alternative. But the CAM spin machine is very effective at spreading misinformation and confusion. They don’t let the facts get in their way.

But the kernel of truth in all of this (the best lies always have a kernel of truth) is that we can do better in modern medicine than we are doing. The problem is not cultural or systemic. I am proud of my profession in that it is conscientiously self-critical and science-based. There are many academics whose job is basically to evaluate and improve the state of evidence in medicine, and then spread the results to the profession at large.

But science-based medicine is hard. We are overwhelmed with evidence and it is impossible to keep up with it all. I think we would benefit from a system of continuing medical education that was more systematic and less haphazard, including methods for educating practitioners about the established evidence-based standards. This happens, I just think we can do better. At the highest levels of academia I think the system actually works impressively well, it’s more that the evidence-based standards need to trickle down more quickly and systematically to practitioners in the field.

As high as the general level of evidence is within mainstream medicine, the general consensus is that we need to continue to push it higher – hence the development of evidence-based medicine, and the constant revision of our standards of practice. CAM proponents, on the other hand, seek only to create a double standard for themselves – one with lower and lower standards of evidence and plausibility for themselves. To cover themselves they promote the fiction that mainstream medicine is not based upon science either – always trying to lower the standard.

That is the real urgent crisis in medicine.

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