Common Sense vs. Evidence-based Medicine

by Tejas Desai, MD
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So much has been said and written about evidence-based medicine as the ultimate form of medical practice that young physicians today have learned medicine in this environment only. It may be hard for these young physicians to believe that there was a time, long ago, when the number of and access to clinical trials and scientific data were scarce and cumbersome. Back then, physicians had to use their common sense to make what they thought were rational medical decisions. It is at the intersection of common sense and evidence-based medicine that I have found myself many times. It’s a fork in the road that I still have difficulty navigating, even more so now that I’ve finished my training.

Why is it that common sense approaches to Nephrology (or Medicine as a whole) aren’t always congruent with evidence-based medicine? Perhaps the “common sense” approach really isn’t all that sensible, but I find that argument hard to swallow. Case in point: consider a patient who is pre-CKD, with a hemoglobin of 13 g/dl, living his/her life and minding his/her own business. Then BAM!!…struck with kidney disease and before you or he/she knows it, the hemoglobin is down to 8 g/dl and because of other considerations, it’s dialysis time. What would the appropriate hemoglobin be now? We’d all agree that the hemoglobin of 8 g/dl isn’t the appropriate level, but wouldn’t you think it should be 13? After all, that’s the hemoglobin level with which he was living before dialysis. In years past, many nephrologists thought the same, applying a common sense approach to this medical decision. We now know that the pre-dialysis hemoglobin level, if above 12 mg/dl, isn’t the appropriate level in an ESRD patient. Four studies (Normal Hematocrit Study, CHOIR, CREATE, and TREAT) have shown that the aforementioned “common sense” approach isn’t supported by the evidence. Patients are more likely to suffer adverse cardiovascular outcomes if their hemoglobin levels are maintained above 12 g/dl, even if they were living at such a level before initiating dialysis. Ask an educated person outside of nephrology what they would do, and I’m sure you’d get some to raise the hemoglobin to 13. Sounds logical, so why isn’t the evidence congruent with what appears to be logical strategy?

I don’t know the answer to this question (among many others). Although we may think our thoughts are logical, human physiology seems to differ with us. I guess I can concede that point; that the body knows more about itself than I do. What scares me, though, is the number of times clinicians make medical decisions with only common sense to support themselves. That’s because there are a lot of questions in nephrology that aren’t answered with clinical trials. Are clinicians making the right decisions in the absence of scientific data? In the absence of this data should we still place such a large amount of faith in our common sense? Would it make more sense to not trust our common sense and look for other ways of answering clinical questions?

I don’t know, and that’s something that the evidence and my common sense both indicate.

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