I am amazed that the longer I practice medicine, the more it looks like real estate. I know that sounds bizarre, but allow me to elaborate. There is a dictum in real estate which says something to the effect that the most important determinant of value is location, location, and location. Ostensibly what this means is the actual structure is really of secondary importance, no matter what anyone has put into it. What is most important is where the structure happens to be placed.
The practice of medicine follows the same rules. Instead of location we deal with context. Information in medicine is critical but information without context is difficult to interpret and potentially dangerous. When I was in training, we still checked serologic tests for syphilis on every patient who was admitted to the hospital. While this practice was perhaps useful at a time where the prevalence of syphilis exposure and occult carriage was significant in the patients who were being admitted, by the time I came along most of the positive blood test that came along were false positives. The screening test was a good test within a certain context but its application needed to remain within that context for it to be useful.
The utility of both diagnostic and therapeutic interventions need to be understood within the context they are validated. In fact, the entire practice of medicine needs to be examined within the context of who we see and why we see them. During the past century, there has been a fundamental change in the types of patients we see and why we see them. We have moved from a model of seeing patients when they clearly identifiable present problems to a model where we see them when they are feeling fine in the hopes that we can keep it that way. Unfortunately, I do not believe we have adequately modified our thinking to account for this dramatic change in context.
There was a time where most patients seen were actually sick. Our physical exam tools were validated (at least to some degree) within those contexts. Similarly, most of our diagnostic tests were validated within specific well defined disease contexts. Rales detected on chest exam within the context of fever and a cough points to pneumonia. A positive RPR within the context of a young sexually active man with a palmar plantar rash is meaningful.
Despite moving to a well patient model, we still do many of the same things to our patients, using tools that have been validated in patients with illness. What is the utility of listening to the chest of an asymptomatic 20 year old? What is the utility of examining every square centimeter of skin in a young, dark-skinned patient with no personal or family history of skin disease? What is the hit rate for relevant findings for any of these routine exams or labs in asymptomatic individuals?
Like real estate and location, the first thing to always consider in medicine is our location equivalent, context. We should not even begin to consider how many baths or how big the yard is until we have clearly defined location, location, location.