Liver Function Tests (LFT)
Liver function tests (LFTs) involve a panel of biochemical tests that includes tests for aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AP), bilirubin, total protein, and albumin. The LFT panel is a misnomer because it does not reflect only liver function; instead, LFTs involve markers of liver cell damage or dysfunction, as well as liver function.
Several factors affect liver enzymes, including age, BMI, muscle mass, lifestyle, and lipid and carbohydrate metabolism. New reference ranges of aminotransferases have been proposed. In adults, the updated upper limits are 500 nkat/L (30 U/L) for males and 317 nkat/L (19 U/L) for females. If the LFT results are abnormal, identification of the duration and pattern of abnormalities is the first step of evaluation. The presence of hyperbilirubinemia, coagulopathy, and hypoalbuminemia is an excellent measure of hepatic function and prognosis and indicates liver failure, which may be acute, subacute, or chronic. A detailed history and examination is the key to the diagnosis and helps avoid unnecessary testing.