Health & Medicine


Diagnosis, in medicine, the determination of the nature of a disease. Modern diagnosis combines the taking of the patient's health history, a physical examination, and laboratory and radiological examinations.

Some diseases, such as measles and mumps, are fairly easy to identify by appearance. Other problems, such as broken bones, are often suspected on the basis of symptoms and confirmed by X-ray observation. With many symptoms, however, more complex testing is needed. Establishing the presence of a gastric ulcer, for example, is helped by inserting a tube called an endoscope into the stomach. Coronary artery disease may be suspected due to the presence of chest pains and an abnormal electrocardiogram (see Electrocardiography); definitive evidence, however, comes only from an angiogram, in which dye is injected into the coronary arteries (see Heart Diseases). A diagnosis of cancer often requires a biopsy, or microscopic examination of tissues. Diagnosis of disease in a fetus is now possible, in many cases, by using sound waves or by sampling amniotic fluid (see Amniocentesis).

Laboratory tests are becoming more important in diagnosis. Measurement of hormone levels identifies endocrine diseases. Enumeration of different kinds of cells in the blood, called a differential count, helps pinpoint anemias and some kinds of cancers. The culturing of body fluids or tissues to show the presence of specific microorganisms is essential to rational treatment of infections with antibiotics (see Antibiotic).

Many diseases, such as headaches, are difficult to diagnose because they may have many causes. Some neurological diseases, such as Huntington's disease, can be identified with certainty only after many years of observing the patient's symptoms. To sharpen their diagnostic skills, physicians and other medical professionals hold regular conferences at which difficult cases are discussed.