Interpreting Liver function tests (LFTs)

Components of the LFT panel

• ALT (alanine aminotransferase): Marker of hepatocellular injury.
• AST (aspartate aminotransferase): Less specific; can be elevated in muscle injury.
• ALP (alkaline phosphatase): Raised in cholestasis; also found in bone.
• GGT (gamma-glutamyl transferase): Helps confirm hepatic source of raised ALP.
• Bilirubin: Elevated in hepatocellular injury or cholestasis.
• Albumin: Low in chronic liver disease or systemic illness.
• Prothrombin time (PT)/INR: May be included; prolonged in synthetic failure.

Initial pattern recognition

• Hepatocellular (↑ ALT/AST): Viral hepatitis, NAFLD, drug-induced liver injury, alcohol.
• Cholestatic (↑ ALP ± GGT): Gallstones, biliary obstruction, PBC, PSC.
• Isolated hyperbilirubinaemia: Consider Gilbert’s syndrome if unconjugated.
• Hypoalbuminaemia: Consider chronic liver disease, nephrotic syndrome, malnutrition.

Common scenarios in primary care

• Isolated mildly raised ALT: Check alcohol use, BMI, metabolic syndrome. Consider NAFLD.
• Raised ALP with normal GGT: Suggests non-hepatic cause, e.g. bone disease.
• Raised ALP and GGT: Suggests biliary disease—consider USS liver and referral if persistent.
• Persistent abnormal LFTs >3 months: Refer for imaging and hepatology work-up (BSG 2017).

Reproduced from : https://gps.northcentrallondon.icb.nhs.uk/pathways/ncl-adult-abnormal-liver-function-tests-primary-care-clinical-pathway