For updates on diagnosis and management of coexisting conditions during the pandemic, see our topic "Management of coexisting conditions in the context of COVID-19".
Serum liver chemistry tests, commonly called liver tests, or (mistakenly) liver function tests, are ordered for many reasons. Most laboratories offer these tests as a bundle, and this usually includes:
Bilirubin (breakdown product of the RBC after conjugation in the liver and secretion in biliary system excretion)
Alanine aminotransferase (ALT)
Alkaline phosphatase (ALP)
The following tests may also be included in this bundle:
Aspartate aminotransferase (AST)
Gamma glutamyl transferase (gamma-GT)
Lactate dehydrogenase (LDH).
Individual tests in these panels are not specific for liver disease. Therefore, pattern recognition is critical. Evaluation of patients with abnormal liver tests should be guided by history, risk for liver disease, duration and severity of clinical findings, presence of comorbidities, and the nature of the liver test abnormality noted.
Traditionally, liver tests abnormalities have been grouped under the following patterns:
Hepatocellular (predominantly ALT and AST elevations)
Cholestatic (predominantly ALP elevation)
Mixed/infiltrative (elevation of both ALT/AST and ALP).
Isolated elevation of liver tests is a less common occurrence in liver diseases, and a nonhepatic source should also be considered in such instances. Bilirubin may be elevated in any category of liver disease. Isolated gamma-GT elevations are so common and so often unhelpful that many institutions have chosen to delete this test from their liver test panel. When other liver tests are abnormal, categorization according to pattern is helpful to determine the probable etiology.
Clinical correlation is essential when interpreting liver tests. Liver tests are abnormally elevated in 1% to 9% of the asymptomatic population. Further investigations with diagnostic serology and liver biopsy are normal in 6% of these patients. Importantly, people with chronic liver disease or cirrhosis may have normal liver tests.
Liver tests are markers of liver injury, not liver function. Functional assessment of the liver (evaluating protein synthesis, metabolism, bile production, storage, and detoxification) can be determined by:
Conventional liver tests such as albumin and INR
Scoring systems such as Model for End-Stage Liver Disease (MELD) and Child-Turcotte-Pugh (CTP) score, based on laboratory test results and clinical features.
- Hepatitis C virus infection
- Hepatitis B virus infection
- Hepatitis A virus infection
- Alcohol-related liver disease
- Acetaminophen overdose
- Nonacetaminophen medications or dietary supplements
- Nonalcoholic fatty liver disease
- Gilbert syndrome
- Hepatitis E
- Hepatitis D
- Epstein-Barr virus infection
- Herpes simplex virus infection
- Cytomegalovirus infection
- HIV infection
- Extrapulmonary tuberculosis
- Alpha-1 antitrypsin deficiency
- Wilson disease
- Autoimmune hepatitis
- Primary biliary cholangitis
- Primary sclerosing cholangitis
- Hepatocellular carcinoma
- Liver metastases
- Pancreatic cancer
- Hodgkin lymphoma
- Non-Hodgkin lymphoma
- Portal vein thrombosis
- Budd-Chiari syndrome
- Intrahepatic cholestasis of pregnancy
- Hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome
- Acute fatty liver of pregnancy
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