History Taking: The Most Important Clinical Test
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History is his/her story and should be heard with the same delight one hears any story. History taking in medicine is probably as old as the practice of medicine itself. It was never considered a test and was therefore never looked at from that point of view. If we accept the definition of a clinical test (Chap. 1), it becomes clear that history taking is a test used to rule in or out a disease and one can even quantify disease by asking the patient if they are better or worse. Studies have shown that it is the most important clinical test one can do to make a diagnosis. In a medical clinic, it was observed that from history alone one could make a diagnosis in 56% of the cases that presented. As a patient walks into the physician’s office, he could have any disease. He gives his presenting complaint and then you have a fair idea of the system involved. Further questioning will start giving the clues as to possible diseases one may be dealing with. From the pre-test probability of near zero as the patient walks into the room you have after history a post-test probability of your differential diagnosis at around 40–50% at least 6 out of 10 cases. What is also useful is that you will order test in such a way that the pre-test probability is high for the disease being tested, and this makes the positive predictive value of the test even more useful.