I recently wrote a Washington Post column about platelet-rich plasma, a treatment highly touted for sports injuries but without much clear evidence. As I later wrote at Last Word On Nothing, PRP provides a case study in why it’s so important to track outcomes in medicine. If you don’t measure your outcomes, you have no way to really know how you’re doing. Humans are notoriously bad at self-evaluating. A 2006 study published in JAMA found that, “physicians have a limited ability to accurately self-assess,” and a 2012 study found that doctors overestimate the value of the care they provide. And if you have an incentive (money?) to keep doing something, results be damned, then if you’re not careful, an ineffective practice can become fixed as the standard of care. Once that happens, it’s very, very difficult to walk it back.