Because the liver performs multiple functions, no single laboratory test or battery of tests is sufficient to provide a complete estimate of the function of the liver in every clinical situation. A broad array of biochemical tests are used to assess the many functions of the liver and to evaluate patients with suspected or established liver disease. These tests are referred to collectively as "liver function tests" (LFTs). LFTs are used to screen people for the presence of liver disease, suggest the underlying cause, estimate the severity, assess prognosis, and monitor the efficacy of therapy. Abnormal LFTs may be the first indication of sub clinical liver disease and may thereby guide further diagnostic evaluation. After the existence of hepatic dysfunction is recognized, the specific pattern of liver test abnormalities may suggest the category of the underlying liver disease, such hepatitis, biliary obstructions, or infiltrative liver disease. The value of screening healthy, asymptomatic persons for liver disease with the use of LFTs is controversial and may not be cost-effective. If screening is performed a panel of tests (e.g., AST, alkaline phosphatase, bilirubin, albumin) is preferable to using a single test because of superior sensitivity and specificity for liver disease and lower cost than the sum of individually performed tests.