FIB-4 Index for Liver Fibrosis

Methodology

FIB-4 (Sterling 2006); MASLD cut-offs (Shah 2009; AASLD 2023)

FIB-4 = age × AST ÷ (platelets × √ALT); cut-offs 1.3 (2.0 if 65+) and 2.67

The lower cut-off is raised to 2.0 at age 65 and over to reduce false positives (McPherson 2017).

Who it is for

Adults with chronic liver disease (e.g. MASLD, hepatitis C), aged 35 and over for MASLD cut-offs.

Version

1.0.1

How this calculator works

Where the formula comes from

• FIB-4 was developed by Sterling and colleagues (2006) from liver biopsies in 832 patients with HIV/hepatitis C coinfection, split into training (555) and validation (277) sets.^[1]
• In that study FIB-4 had an AUROC of 0.765 for advanced fibrosis (Ishak 4–6); a value below 1.45 had a negative predictive value of 90% and a value above 3.25 had a specificity of 97%.^[1]

The inputs

• FIB-4 = age (years) × AST (U/L) ÷ (platelets (10⁹/L) × √ALT (U/L)).^[1]

Versions and alternatives

• In NAFLD, Shah and colleagues (2009) used cut-offs of 1.30 to exclude and 2.67 to suggest advanced fibrosis.^[2]
• McPherson and colleagues (2017) proposed a lower cut-off of 2.0 for people aged 65 and over to reduce false positives.^[3]

Where accuracy falls (published evidence)

• FIB-4 had low accuracy in people younger than 35; in older adults, the age term raises the score and reduces specificity at the usual cut-off.^[3]
• The AASLD 2023 guidance advises not to use FIB-4 in acutely ill patients.^[4]

What guidelines say

• AASLD 2023 recommends FIB-4 as the initial assessment of advanced fibrosis risk in people with or at risk of NAFLD/MASLD; a result of 1.3 or more generally prompts a second test such as vibration-controlled transient elastography or ELF.^[4]

Sources

1. 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. doi:10.1002/hep.21178
2. 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. doi:10.1016/j.cgh.2009.05.033
3. 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. doi:10.1038/ajg.2016.453
4. 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. doi:10.1097/HEP.0000000000000323

Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on 2026-10-11

Worked example: how to calculate FIB-4

An illustration with sample values, worked out with the same method the tool above uses.

Limitations

• Less accurate under 35 years; not for use in acutely ill patients (AASLD 2023).

References

1. 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. doi:10.1002/hep.21178
2. 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. doi:10.1016/j.cgh.2009.05.033
3. 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. doi:10.1097/HEP.0000000000000323
4. 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. doi:10.1038/ajg.2016.453