What are the steps my doctor needs to take to make a diagnosis?

Long before a doctor ever orders a test, writes a prescription or lifts a scalpel, there is that pivotal symptom hinting that something is not right. It will eventually become what doctors call the "chief complaint," the symptom or constellation of symptoms that guide them down a particular diagnostic path. The process is arduous. Many diseases have similar symptoms while few have symptoms that are unique to one. Doctors must aggregate all the signs and symptoms, see if the person also falls into a high risk group, generate a list of possible causes, prune the list, and then validate everything to arrive at a definitive diagnosis.