In this post, I will put forth my argument that evidence based medicine is a paradigm, and as such, it has limitations. Medical schools and medical practice have been strongly touting evidence based medicine as the ideal way to go about being a doctor. In evidence based medicine, the best practice is determined by the strength of the clinical studies supporting it. It is a uniform way to take all the data published, weigh it by how good it is (ie. whether it was a double blind randomized control trial) and then recommend to doctors what they should do. These studies often use endpoints such as mortality, morbidity, quality of life, complications, etc. For example, why are beta-blockers given in congestive heart failure? Because the MERIT-HF study demonstrated a 34% decrease in all cause mortality after administration of Metoprolol CR/XL in patients with stable New York Heart Association class II-IV congestive heart failure receiving standard medical therapy. This is supported by other trials such as the CIBIS I, CIBIS II, Carvedilol Clinical Trial Program, and COPERNICUS. Evidence based medicine uses these publications to support the administration of beta-blockers in heart failure.
But I have reservations about this paradigm of evidence based medicine. Its assumption is that medicine is justified if evidence shows it improves outcomes. This may seem very self-evident. But I believe this assumption has a lot of problems.
For example, our justification for giving beta-blockers in CHF makes no mention of molecular mechanism of action or reversal of pathophysiology or any basic science whatsoever. Evidence based medicine looks only at well-designed clinical trials. But we don't really have a clear idea why beta blockers actually work. They might reduce oxygen utilization, prevent dislodging of coronary plaques, increase the threshold for ventricular fibrillation in the presence of ischemia (atenolol and bisoprolol), reduce detrimental myocardial remodeling (all beta blockers), reverse abnormal intracellular calcium handling, enhance secretion of atrial natriuretic peptide (carvedilol), or increase myocardial endothelial nitric oxide synthase (eNOS). Or any combination of these mechanisms. But does this paradigm of medicine care?
Evidence based medicine hamstrings basic science by saying it doesn't matter why things work as long as they do. If someone randomly finds a compound that cures a disease and shows it through the right clinical trials, it doesn't matter if we have no idea how that compound works. That bothers me. This paradigm discourages scientists from thinking from first principles (which I admit is philosophy, probably explaining why this bothers me so). True, first principles may eventually give rise to clinical evidence, but there's no value in first principles in and of themselves. That's something in the domain of science, not in this paradigm of medicine.
Nevertheless, evidence based medicine saves more patients than thinking from first principles. Indeed, in congestive heart failure, the heart isn't squeezing hard enough and you might think that to save the patient, you want to squeeze it harder - that is, give a beta-agonist or inotrope. It makes scientific sense and it failed miserably. We now do the counter-intuitive thing by giving beta-blockers which decrease the contractile force of the heart. But this simply means we haven't fully understood the complexity of molecular cardiology and should motivate us to pursue the basic labwork necessary to elucidate this system.
Perhaps we're not ready for a new paradigm. We don't have enough understanding of the basic sciences to use that to justify our medical decisions. Indeed, evidence based medicine will save more patients because that's what it's built around. But does it teach us to have the right attitude toward how basic science drives medicine? I'm not so sure on that account.
Most of the science in this post is drawn from a lecture entitled "Beta-blockers: How do they really work?" by Dr. Patterson from Stanford University. There are also several other problems with evidence based medicine, such as the problem of induction, which I don't have the room to discuss.
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3 comments:
I like this post also
I don't think EBM discourages basic scientists from thinking from first principles. At least from a philosophical standpoint.. maybe you could argue about diverted NIH funding, etc. But the medical paradigm is sufficiently complicated that going from first principles is often impossible. In this lifetime, maybe it's best to just keep morbidity rates low.
And to jump to your philosophy angle, what do you think of Kant's transcendental method? Kant asserts that no kind of empirical psychology can yield necessary truths about the mind. In light of this limitation, how should we study the mind? Kant's answer was: If we cannot observe the connections among the denizens of inner sense to any purpose, we can study what the mind must be like and what capacities and structures it must have if it is to work the way it does. With this method, we can find universally true 'transcendental' propositions, that do not derive from the inner workings. I think in a way, EBM and much of the medical paradigm applies the transcendental method not to the mind, but to the body.
You're right in that the medical paradigm is sufficiently complicated that going from first principles seems impossible. But then, one could argue that high throughput drug design - blindly testing lots and lots of compounds - could yield "better" results than designing a drug based on first principles. And I'm not sure I like that. I'd rather ally medicine with science rather than with random shotgun screening. Whether one is justified by leading to better results is based entirely on the paradigm in which you're operating.
The point about Kant's transcendental method is interesting. I don't know enough about his position on empirical psychology. Indeed, Kant oriented his Critique of Pure Reason against Hume's very empirical stance. Certainly at that time, much of the mind defied empirical study; it does not seem to fit neatly into the "form" of matter ("that which so determines the manifold of appearance that it allows of being ordered in certain relations"). Whether the mind and its faculties are subject to space and time has been a perennial question in philosophy. How we are to go about understanding the mind in a scientific fashion, I cannot say. Certainly now, there are scientific methods for probing the mind and its "connections among the denizens of inner sense." Whether these will ever be adequate for understanding the mind in the same way as we understand say renal physiology, I don't know.
Whether EBM applies the transcendental method to the body, I'm skeptical. I don't think to study the body, we infer the conditions necessary for that body to operate. But I may either be misinterpreting Kant or the scientific method or both. Certainly, science uses inference to the best explanation, but it is not postulating unobservable mechanisms in order to explain observed behavior. I'm not sure medical science is trying to unearth necessarily true propositions about the body at this time.
I'm hardly versed in this subject. A good discussion can be found at the Stanford Encyclopedia of Philosophy here:
http://plato.stanford.edu/entries/kant-mind/
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