Diagnosis - Patient Information, The Physical Examination, The Laboratory Examination

Diagnosis, from gnosis, the Greek word for knowledge, is the process of identifying a disease or disorder in a person by examining the person and studying the results of medical tests.

The diagnosis begins when the patient is presented to the doctor with a set of symptoms or perceived abnormalities such as pain, nausea, fever, or other untoward feeling. Often the diagnosis is relatively simple, and the physician can arrive at a clinical conclusion and prescribe the proper treatment. At other times, the symptoms may be subtle and seemingly unrelated, making the diagnosis difficult to finalize and requiring laboratory work.

The diagnosis is based on data the physician obtains from three sources, the first being the patient. This includes the patient's perception of his or her symptoms, medical history, family history, occupation, and other relevant facts. The physician then narrows the diagnosis with a second set of information obtained from the physical examination of the patient. The third source is the data obtained from medical tests, such as a blood test, x ray, or an electrocardiogram.