Once the examination is complete and the necessary tests have been performed, a “differential diagnosis” is established. This is simply a list of all the possible diagnoses that could explain the patient’s problem. Depending on the nature of the problem, this list may be quite short or relatively long. As an example, in the case of an ankle fracture the list would only have one possible diagnosis on it. However, if the complaint was “knee pain”, the list may include 10 to 15 possible diagnoses.
Given a differential diagnosis, various means are used to narrow down the list. Other tests may be obtained such as blood tests or special imaging studies. Occasionally it is best to just wait and observe a certain condition and time alone will help elucidate the diagnosis. Sometimes a “clinical trial” is done. This is when a diagnosis is presumed and the specific treatment for that problem is administered. If the patient’s response to that treatment is positive, the presumed diagnosis is considered to have been correct. Rarely, a diagnostic surgical procedure is necessary to come to the correct diagnosis, although in such cases, the treatment for the problem is generally performed at the same time.