Abnormal Liver Tests

The term "liver function tests" (often abbreviated to "LFTs" by your doctor) is a commonly used term applied to a variety of blood tests that reflect the general state of the liver and biliary system.

Routine blood tests can be either tests that are simply markers of liver or biliary tract injury (the liver enzymes tests), or true LFTs, such as serum albumin or prothrombin time. In addition, your doctor may order specific liver tests that if positive, can determine the specific cause of liver disease.

What do liver enzyme tests show?

There are two general categories of "liver enzymes". The first group includes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), formerly referred to as the SGPT and SGOT respectively. These enzymes are indicators of liver cell damage or hepatitis. The second group of liver enzymes are alkaline phosphatase (ALP) and gammaglutamyltranspeptidase (GGT) - these indicate obstruction to the biliary system or cholestasis, either within the liver or in the larger bile channels outside the liver. However, both liver and biliary disease often cause a simultaneous disturbance of the liver enzymes indicating liver cell damage and jobstruction of the biliary system. Finally, the bilirubin level is elevated in people with jaundice.

When do abnormal liver enzyme tests need to be elevated?

Abnormal liver enzyme tests are frequently discovered on routine blood testing often as part of a regular medical checkup and may not be of any clinical significance. The normal range quoted by the laboratory is the mean value in a group of healthy people ±2 SD. Thus, 5 percent of the results from normal people fall outside the normal range of which 2.5 percent will be above the normal range. If the liver enzyme test elevation is minor (less than twice the upper limit of normal) and the person asymptomatic it is most appropriate to repeat the liver enzyme tests after an interval of one to two months. If the liver enzyme test elevation persists then your doctor would usually undertake further laboratory and/or radiological investigations to determine the cause. Evaluation of an isolated evaluation of ALT or AST differs from that for someone with an isolated elevation of ALP or GGT. Evidence of liver synthetic failure such as a low albumin or prolonged prothrombin ratio should prompt urgent evaluation and referral to a gastroenterologist or liver specialist.

What are the cause of abnormal liver enzyme tests?

There multiple possible cause of elevated liver enzyme tests and the differential diagnosis varies with age. Common causes of hepatitis in adults are fatty liver, viral hepatitis, prescribed and nonprescribed drugs including alcohol. The most common cause of cholestasis is bile duct obstruction from gallstones or narrowing of the bile ducts and drugs.

See also patient information on cirrhosis.