De-mystifying Evidence Based Medicine

Evidence based medicine (EBM) is a real buzzword right now. I had never heard the term until I was in the lecture hall during my first year of medical school. “Isn’t all medicine based on evidence?” I wondered. This blog post will help both you and I to better understand what it means, and why it matters.

To misquote David Foster Wallace: “Ask a fish how the water is and it will say ‘what the hell is water?’” Similarly, when Dr. Moses first asked my OMS-I class how to apply EBM, I also had to ask, “What the HELL is EBM??” And I still ask that question weekly. In my experience as a patient, I got my vaccines to avoid getting chicken pox, measles, mumps, rubella, tetanus, and the flu every year. For my rare heart and lung condition, I was prescribed medications that had been tested through clinical trials. I saw my parents go get their first colonoscopies at age 50, to prevent advanced colorectal cancer which is typically seen in older adults. Don’t we do all these things because there is quantifiable benefit in doing them? How do you define medicine as anything but “medicine”? 

EBM has more than one formal definition. Two are selected here. EBM was first formally defined in 1990 in the context of writing medical policies and guidelines at the level of national medical associations as: 

“explicitly describing the available evidence that pertains to a policy and tying the policy to evidence instead of standard-of-care practices or the beliefs of experts. The pertinent evidence must be identified, described, and analyzed. The policymakers must determine whether the policy is justified by the evidence. A rationale must be written.”

Then in 1996, it was defined in the context of individual care as:

“the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.”

These two definitions both point to the use of clinical trials, published data that was gathered using the scientific method, and likely the use of appropriate peer review. It’s coming together, but I still do not understand why we have a special name for this topic.

The existence of EBM implies the existence of “non-evidence-based medicine” (nonEBM for our purposes). An obvious practice of nonEBM is the outdated practice of bloodletting. Wikipedia tells me: “Bloodletting is varied in its practices cross-culturally, for example, in native Alaskan culture bloodletting was practiced for different indications, using different tools, on different body areas, by different people, and it was explained by different medical theories.” This definition points to one thing: lack of consistency. Studying the effectiveness of bloodletting on different diseases, and the best way to perform it, may well lead a team of researchers to the answer that bloodletting is only effective in a few cases, and is best performed with clean needles in a well-controlled way. This is called therapeutic phlebotomy instead of bloodletting, and is a common, evidence-based treatment for a small handful of conditions. I am finally beginning to understand EBM as common-practice medicine that makes sense because of consistency and data to back up the claim of consistency.

The generation of physicians before me, and certainly the ones before them, saw the ushering in of EBM, assisted in large part by the dawn of the internet. One person cannot know every detail of medicine and what the scientific evidence on that topic reveals. MDCalc, and WikiEM are all resources we reach to often in class and in the office. It took me a full three and a half semesters in medical school to realize these two apps are just tools to apply EBM practices. Internal medicine and FM faculty would more commonly point to UpToDate, a more robust yet long-winded source of guidelines and explanations for diagnostic and treatment methods. My point is, for medical students in 2024, EBM is so ubiquitous that it seems silly to even define it.

If you had no idea what EBM means, you are not alone. If you still have no idea, you are also probably not alone. I think I am getting an understanding of it, and more importantly, an appreciation for why it is discussed so often without ever really being defined. To hearken back to Mr. Foster, we in medical school are fish, and EBM is water. You’d have to try pretty hard to avoid it, and without it, you wouldn’t get very far as a medical student or physician.

Some references

https://en.wikipedia.org/wiki/Evidence-based_medicine

Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS (January 1996). “Evidence based medicine: what it is and what it isn’t”. BMJ. 312 (7023): 71–72. doi:10.1136/bmj.312.7023.71. PMC 2349778. PMID 8555924.

Eddy DM (April 1990). “Clinical decision making: from theory to practice. Practice policies—guidelines for methods”. JAMA. 263 (13): 1839–1841. doi:10.1001/jama.263.13.1839. PMID 2313855.
https://www.tandfonline.com/doi/full/10.2147/JBM.S108479