Reliability of the clinical examination: how close is "close enough"?

It is has been said that close only counts in a game of horseshoes. The reason being, of course, that when playing horseshoes you get points for having the shoe closest to the stake even if it isn't touching. In reality, this saying is true for many psychomotor activities. For example, a baseball pitch only counts as a strike if it is within the strike zone, a thrown dart counts as a bull's-eye only if it hits somewhere within the red center, and a field goal in football is only worth 3 points if it passes between the uprights. In each of these tasks, there is a certain margin of error that is acceptable, and the margin of error for each has been operationally defined. Likewise, the clinical examination, which is comprised of the history and physical examination, consists of psychomotor tasks that are performed on a regular basis by all practicing clinicians. The ultimate goal, of course, is to accurately establish a diagnosis, direct the choice of intervention, and establish a prognosis. The practical qu...