Evaluating abnormal liver tests



The degree and pattern of liver tests’ elevation may provide clues as to aetiology (Figure 30.1). A practically useful classification is provided below.

Liver test abnormalities are designated as:

In the vast majority of patients with liver disease, the serum ALT exceeds the AST. Exceptions include those with alcoholic liver disease and those with cirrhosis from any aetiology.

The presence of liver test abnormalities in association with a low serum albumin or a prolonged prothrombin time infers significantly impaired hepatic synthetic function, while an elevated bilirubin reflects hepatic excretory dysfunction.

Disorders associated principally with elevations in aminotransferase levels

Aminotransferase levels are sensitive indicators of hepatic injury; ALT and AST are present normally in serum at low levels, usually less than 30–40 U/L.

AST is found in:

Because the highest levels of ALT are in the liver, an elevation of ALT is a more specific indicator of liver injury than the AST.

Common causes of liver enzyme abnormalities according to the pattern of enzyme elevation are presented in Table 30.1.

TABLE 30.1 Causes of elevated liver enzyme levels

Hepatocellular Cholestatic
Excessive alcohol consumption Drug-induced liver injury
Drug-induced liver disease Choledocholithiasis
Chronic hepatitis B and C Primary biliary cirrhosis
Non-alcoholic fatty liver disease Primary sclerosing cholangitis
Haemochromatosis Pancreatic carcinoma
Autoimmune hepatitis Neoplastic infiltration
Wilson’s disease Sarcoidosis
Alpha1-antitrypsin deficiency  

Additional laboratory tests useful in identifying specific disorders are listed in Table 30.2.

TABLE 30.2 Laboratory tests to clarify the cause of liver test abnormalities

Laboratory test Diagnosis
Hepatitis C antibody Positive test suggests chronic hepatitis C infection
Hepatitis B surface antigen Positive test suggests chronic hepatitis B infection
Hepatitis B e antigen Positive test suggests active viral replication
Serum ferritin, transferrin saturation Iron overload suggests haemochromatosis
Antimitochondrial antibodies Detected in primary biliary cirrhosis
Antinuclear antibodies, anti-smooth muscle antibodies Detected in autoimmune hepatitis
Serum caeruloplasmin Reduced in Wilson’s disease
Serum alpha1-antitrypsin Decreased in alpha1-antitrypsin deficiency

Mar 29, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Evaluating abnormal liver tests
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