** A chronological basis for patient records **
The term “Diagnosis” encompasses determining the nature of a disease. Diagnosis must combine an adequate clinical history (personal and family history, and current illness), a complete physical examination, and complementary examinations (laboratory tests and diagnostic imaging).
Some diseases such as measles and mumps are easily identified by their appearance. Other problems such as bone fractures can be suspected by their symptoms and signs, and are confirmed by X-rays. But many symptoms require a more complex diagnostic procedure. Confirmation of a gastric ulcer, for example, requires the introduction of an endoscope into the stomach. Coronary disease can be suspected by the characteristics of the pain and by electrocardiographic changes, but definitive evidence can only be obtained by coronary angiography, a technique in which a contrast substance is injected into the coronary arteries that supply blood to the heart. Diagnosing many types of cancer requires a biopsy, which is a sample of affected tissue for microscopic examination. Diagnosing a number of fetal diseases is now possible by ultrasound or by analysis of amniotic fluid obtained by amniocentesis.
Laboratory tests are becoming increasingly important. Measuring hormone levels identifies endocrine disorders. Counting the different types of blood cells, called differential counts, is used to diagnose different types of anemia and some types of leukemia and other cancers. Microbiological cultures of fluids and tissues are used to identify the microorganisms that cause infectious diseases and are essential for rational treatment with antibiotics.
Many diseases, such as headaches, are difficult to diagnose because they can be caused by many different things. Some neurological diseases, such as multiple sclerosis and Huntington's chorea, can only be identified with certainty after several years of clinical observation of the patient. To refine their diagnoses, doctors and other health care professionals hold regular meetings (called clinical sessions) in which difficult-to-solve cases are discussed.





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