{
  "id": "fib-4",
  "version": "dca4d7ad8725",
  "status": "published",
  "name": "FIB-4 Calculator",
  "question": "What is my FIB-4 score?",
  "summary": "Calculates the FIB-4 liver fibrosis index from age, AST, ALT, and platelet count (Sterling 2006) and reads it with the published cut-offs for fatty liver disease (MASLD) or for hepatitis C and HIV.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/fib-4-calculator",
  "markdown": "https://www.acalculator.org/health/fib-4-calculator.md",
  "kind": "function",
  "method": "FIB-4 = (age × AST) ÷ (platelets × √ALT), with AST and ALT in U/L and platelets in 10⁹/L.",
  "assumptions": [
    "The index is rounded to 2 decimals and read from the rounded value.",
    "MASLD: under 1.30 low (under 2.00 at age 65 or older), over 2.67 high (Shah 2009, McPherson 2017, AASLD 2023). Hepatitis C or HIV: under 1.45 low, over 3.25 high (Sterling 2006).",
    "FIB-4 is less accurate under age 35 and in acute hepatitis."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "for": {
        "title": "Liver condition",
        "description": "Which cut-offs to read the score with: fatty liver disease (MASLD or NAFLD), or hepatitis C and HIV.",
        "type": "string",
        "enum": [
          "masld",
          "hcv"
        ]
      },
      "age": {
        "title": "Age",
        "description": "Age in whole years.",
        "type": "integer",
        "minimum": 18,
        "maximum": 110
      },
      "ast": {
        "title": "AST (U/L)",
        "description": "Aspartate aminotransferase from the blood test, in units per liter.",
        "type": "number",
        "minimum": 1,
        "maximum": 10000
      },
      "alt": {
        "title": "ALT (U/L)",
        "description": "Alanine aminotransferase from the blood test, in units per liter.",
        "type": "number",
        "minimum": 1,
        "maximum": 10000
      },
      "plt": {
        "title": "Platelets (×10⁹/L)",
        "description": "Platelet count in 10⁹ per liter, the same number as 10³ per microliter. 210,000/µL is 210.",
        "type": "number",
        "minimum": 1,
        "maximum": 2000
      }
    }
  },
  "outputs": {
    "fib4": {
      "label": "FIB-4",
      "description": "The FIB-4 index, to 2 decimals.",
      "format": "number"
    },
    "reading": {
      "label": "What the cut-offs say",
      "description": "How the published cut-offs for the chosen condition read the score.",
      "format": "text"
    },
    "cutoffs": {
      "label": "Cut-offs used",
      "description": "The low and high cut-offs applied.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "for": "masld",
      "age": 55,
      "ast": 40,
      "alt": 35,
      "plt": 210
    },
    "outputs": {
      "fib4": 1.77,
      "reading": "Indeterminate: further testing is often needed",
      "cutoffs": "under 1.30 low, over 2.67 high"
    },
    "text": "The FIB-4 index is 1.77. Indeterminate: further testing is often needed."
  },
  "examples": [
    {
      "given": {
        "for": "masld",
        "age": 55,
        "ast": 40,
        "alt": 35,
        "plt": 210
      },
      "expect": {
        "fib4": 1.77,
        "reading": "Indeterminate: further testing is often needed"
      },
      "source": "Sterling 2006: FIB-4 = (55 × 40) ÷ (210 × √35) = 1.7709, shown as 1.77; MASLD cut-offs 1.30 and 2.67 (Shah 2009) (hand calculation in content.mdx)"
    },
    {
      "given": {
        "for": "masld",
        "age": 45,
        "ast": 25,
        "alt": 30,
        "plt": 250
      },
      "expect": {
        "fib4": 0.82,
        "reading": "Low: advanced fibrosis is unlikely"
      },
      "source": "(45 × 25) ÷ (250 × √30) = 0.8216, under 1.30 (hand calculation in content.mdx)"
    },
    {
      "given": {
        "for": "hcv",
        "age": 62,
        "ast": 90,
        "alt": 60,
        "plt": 110
      },
      "expect": {
        "fib4": 6.55,
        "reading": "High: advanced fibrosis is likely"
      },
      "source": "(62 × 90) ÷ (110 × √60) = 6.5490, over 3.25 (Sterling 2006) (hand calculation in content.mdx)"
    },
    {
      "given": {
        "for": "masld",
        "age": 70,
        "ast": 30,
        "alt": 25,
        "plt": 200
      },
      "expect": {
        "fib4": 2.1,
        "reading": "Indeterminate: further testing is often needed",
        "cutoffs": "under 2.00 low, over 2.67 high"
      },
      "source": "(70 × 30) ÷ (200 × √25) = 2.10; at 65 or older the low MASLD cut-off is 2.0 (McPherson 2017), so indeterminate (hand calculation)"
    }
  ],
  "sources": [
    "Sterling RK, Lissen E, Clumeck N, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology. 2006;43(6):1317-1325. https://doi.org/10.1002/hep.21178",
    "Shah AG, Lydecker A, Murray K, et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 2009;7(10):1104-1112. https://doi.org/10.1016/j.cgh.2009.05.033",
    "McPherson S, Hardy T, Dufour JF, et al. Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol. 2017;112(5):740-751. https://doi.org/10.1038/ajg.2016.453",
    "Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology. 2023;77(5):1797-1835. https://doi.org/10.1097/HEP.0000000000000323"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-29",
      "note": "Published after this site's editorial review against the cited sources (no clinician review); the page notice says so."
    }
  ]
}