FIB-4 Index

Non-invasive estimate of hepatic fibrosis in chronic liver disease (NAFLD, HCV, HBV)

Indication

Non-invasive estimate of hepatic fibrosis in chronic liver disease (NAFLD, HCV, HBV)

id: age; label: Age (years); type: number; min: 18; max: 120; step: 1
id: ast; label: AST (U/L); type: number; min: 1; max: 2000; step: 1
id: alt; label: ALT (U/L); type: number; min: 1; max: 2000; step: 1
id: platelets; label: Platelets (10⁹/L); type: number; min: 1; max: 1000; step: 1

function(score, vals) { var a = parseFloat(vals.age) || 50; var ast = parseFloat(vals.ast) || 30; var alt = parseFloat(vals.alt) || 30; var plt = parseFloat(vals.platelets) || 200; var fib4 = (a * ast) / (plt * Math.sqrt(alt)); fib4 = Math.round(fib4 * 100) / 100; if (fib4 < 1.30) return { risk: 'FIB-4: ' + fib4, tier: 'Low Risk', action: 'Low probability of advanced fibrosis (F3-F4). NPV >90%. Repeat in 1-2 years.', color: 'green' }; if (fib4 <= 2.67) return { risk: 'FIB-4: ' + fib4, tier: 'Indeterminate', action: 'Consider additional testing: transient elastography (FibroScan) or ELF test.', color: 'yellow' }; return { risk: 'FIB-4: ' + fib4, tier: 'High Risk', action: 'High probability of advanced fibrosis. PPV ~65%. Refer for hepatology evaluation.', color: 'red' }; }

FIB-4 < 1.30 has NPV > 90% for excluding advanced fibrosis
Less reliable in patients < 35 or > 65 years old
Can be falsely elevated by high AST from non-hepatic sources (muscle, hemolysis)