Hepatic Function Assessment

Hepatic function assessment uses a panel of serum tests to evaluate liver injury, cholestasis, and synthetic capacity. The common analytes include the aminotransferases (ALT and AST), alkaline phosphatase, gamma-glutamyl transferase, bilirubin, albumin, and prothrombin time, each reflecting a different aspect of liver health.

Definition

Hepatic function assessment is the measurement and interpretation of serum markers of liver-cell injury, biliary obstruction, and hepatic synthetic and excretory capacity.

Scope

The topic covers the standard liver test panel and how its components group into patterns of hepatocellular injury, cholestasis, and impaired synthetic function. It also notes that some commonly named 'liver function tests' actually reflect injury rather than function. It is framed as a laboratory-medicine reference and does not provide diagnostic cut-offs or management advice.

Core questions

• Which analytes reflect hepatocellular injury versus cholestasis versus synthetic function?
• Why are aminotransferases markers of injury rather than of function?
• How do albumin and prothrombin time indicate the liver's synthetic capacity?
• How are simple analyte ratios used to estimate hepatic fibrosis non-invasively?

Key concepts

• Aminotransferases (ALT, AST)
• Alkaline phosphatase and gamma-glutamyl transferase
• Bilirubin (conjugated and unconjugated)
• Albumin and prothrombin time as synthetic markers
• Hepatocellular versus cholestatic pattern
• Non-invasive fibrosis indices (e.g., FIB-4)

Mechanisms

Aminotransferases are intracellular hepatocyte enzymes released into serum when liver cells are injured, so their elevation marks hepatocellular damage rather than function per se (pratt-2000). Alkaline phosphatase and gamma-glutamyl transferase rise predominantly in cholestasis, while bilirubin reflects the balance of haem breakdown, hepatic conjugation, and biliary excretion. True synthetic function is gauged by albumin concentration and by the prothrombin time, which depends on hepatically produced clotting factors. Combinations of routine analytes, such as the FIB-4 index that incorporates aminotransferases, platelet count, and age, are used to estimate hepatic fibrosis without biopsy (vallet-pichard-2007; rifai-tietz-2017).

Clinical relevance

Liver test panels are a first-line tool for detecting and characterising liver disease and for monitoring its course. This entry explains what each component represents and how the pattern, rather than any single value, conveys information; it is a reference resource and does not provide diagnostic thresholds or treatment guidance for any individual.

Evidence & guidelines

The interpretation of abnormal liver enzymes as hepatocellular or cholestatic patterns follows established clinical reviews and reference texts (pratt-2000; rifai-tietz-2017), and non-invasive fibrosis estimation from routine analytes is supported by validation studies such as those of the FIB-4 index (vallet-pichard-2007).

Seminal works

• pratt-2000
• rifai-tietz-2017

Frequently asked questions

Are 'liver function tests' actually measuring liver function?

Only partly; aminotransferases and alkaline phosphatase indicate cell injury or cholestasis, while genuine synthetic function is reflected by albumin and the prothrombin time.

What distinguishes a hepatocellular from a cholestatic pattern?

A predominant rise in aminotransferases suggests hepatocellular injury, whereas a predominant rise in alkaline phosphatase and gamma-glutamyl transferase suggests a cholestatic process; the pattern guides further evaluation.