Bayes’s theorem estimates the probability of an event occurring if another one occurred before. If we hear thunder, it’s very likely that soon it will start to rain. However, biomedicine is more interested by the inverse probabilistic formulation because often when an observation is made we look for the cause: "If, for example, you find yourself on a ranch in Texas and hear the sound of trotting horses, what is the probability that a herd of zebras will approach? ”Dr. Saurabh Jha, radiologist, blogger and contributor to the BMJ, says that we hunted zebras in Texas for long enough. "The clinical reasoning of many doctors today - explains Dr. Jha - forgot the Bayesian thinking and embraced instead the thesis that it’s better to manage a false positive than a false negative."
When, in the second decade of the last century, he was asked why he wanted to climb Everest, George Mallory, an English mountaineer, replied that it’s because the mountain was there. According to Dr. Jha, many doctors feel the same as Mallory: they ask for tests because they can. In his article in the BMJ, the radiologist explained the case of a patient of Dr. Watson, a well read doctor emerged from a refined education who pays a lot of attention to detail but lacks the deductive ability of the famous Sherlock Holmes’ assistant. If you have a chance to read the letter, you will see how for the study of this case, nothing seems elementary to Dr. Watson, to the extent that for every horse he sees an opportunity for a zebra hunt. "Zebras are intellectually exciting," Dr. Jha ends up saying.
