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The clinician's main task is to make reasoned decisions about patient care despite incomplete clinical information and uncertainty about clinical outcomes. Although data elicited from the history and physical examination are often sufficient for making a diagnosis or for guiding therapy, more information may be required. In these situations, clinicians often turn to diagnostic tests for help.
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When used appropriately, diagnostic tests can be of great assistance to the clinician. Tests can be helpful for screening, ie, to identify risk factors for disease and to detect occult disease in asymptomatic persons. Identification of risk factors may allow early intervention to prevent disease occurrence, and early detection of occult disease may reduce disease morbidity and mortality through early treatment. Blood pressure measurement is recommended for preventive care of asymptomatic low risk adults. Screening for breast, cervix, and colon cancer is also recommended, whereas screening for prostate cancer and lung cancer remains controversial. Optimal screening tests should meet the criteria listed in Table 1–1.
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Tests can also be helpful for diagnosis, ie, to help establish or exclude the presence of disease in symptomatic persons. Some tests assist in early diagnosis after onset of symptoms and signs; others assist in developing a differential diagnosis; others help determine the ...