FIB-4 Calculator

Also known as FIB-4, Fibrosis-4, FIB4

Screening index for advanced hepatic fibrosis from four routine values.

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Applies to / doesn’t apply to4

Applies to: Adults with suspected or at-risk metabolic liver disease (MASLD/NAFLD), as a first-line non-invasive test. The index was derived in adults with HIV/HCV co-infection (Sterling 2006); the cut-offs shown here come from a biopsy cohort of 541 adults with NAFLD (Shah 2009).

Does not apply if:
  • Adults under 35, in whom accuracy is low and no validated threshold is published (AASLD 2023; ADA 2026). The value is still calculated but is shown without a band.
  • Chronic hepatitis B, where the one published age-banded cut-off set had an AUROC of 0.57–0.65.
  • Alcohol-related liver disease, for which no FIB-4 cut-off pair could be sourced.
  • Severe obesity, where the standard cut-offs gave an AUC of 0.575 in 632 bariatric patients (Green 2024).
FIB-4 inputs
Age

An exact age is required: age multiplies through the formula and also selects the lower threshold (2.00 from age 65). Below 35 no validated cut-off exists, so the value is shown without a band.

years
AST

Aspartate aminotransferase, as measured.

U/L
ALT

Alanine aminotransferase, as measured. A normal ALT does not exclude advanced fibrosis.

U/L
Platelet count

In × 10⁹/L, which is the same number as × 10³/µL. A count of 200,000 cells/µL is entered as 200.

× 10⁹/L

What this score estimates

A screening index for advanced hepatic fibrosis in adults with suspected or at-risk metabolic liver disease (MASLD/NAFLD), computed from age, AST, ALT and platelet count. The result is reported to two decimal places and read against Shah 2009’s cut-offs of 1.30 and 2.67 for advanced fibrosis (NASH CRN stage 3–4 on liver biopsy), with the lower cut-off raised to 2.00 at age 65 and above. Below age 35 no validated cut-off exists, so the value is shown without a band. It is not a fibrosis stage and not a probability.

Pearls & pitfalls

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  • A normal ALT does not exclude advanced fibrosis: 18 of 51 (35%) biopsied NAFLD patients with a normal ALT had bridging fibrosis or cirrhosis (Mofrad 2003), and 78.7% of FIB-4-positive US primary-care patients had normal aminotransferases (Xiao 2025). Because ALT is in the denominator, a lower ALT raises the index.
  • It performs worst in the population primary care is asked to screen. In 1,157 adults with type 2 diabetes and biopsy-proven NAFLD, sensitivity above 2.67 was 6.7% (Singh 2020); in a safety-net fatty-liver cohort the c-statistic was 0.68 with diabetes versus 0.85 without (Kim 2022).
  • It is a rule-out test rather than a rule-in test. In a general ambulatory population the PPV at 1.30 was 5% while the NPV was 98% (Mahady 2017, transient-elastography reference), and in Shah 2009 the upper cut-off of 2.67 had a sensitivity of only 33%.
  • About 30% of results fall in the indeterminate range, where the index is uninformative (163 of 541 in Shah 2009; 17–30% across other cohorts).
  • FIB-4 rises with age independently of fibrosis. In adults 65 and over the specificity of the 1.30 cut-off falls to about 35% (McPherson 2017), which is the reason for the age-adjusted lower cut-off of 2.00.
  • The age adjustment is contested. It rests on a single primary source with a 76-patient stratum (McPherson 2017); it appears only in figure legends and narrative text, never in a graded guideline recommendation; raising the lower cut-off to 2.00 lowered the NPV from 100% to 83% in a primary-care elastography cohort (Moctezuma-Velázquez 2024); and one primary source found that age does not relevantly modify FIB-4 at 1.3 (Sung 2024). Guidelines also differ on whether the boundary is 65 and over or over 65; this page applies it from age 65.
  • Any cause of a low or high platelet count unrelated to liver disease moves the result, because platelets are in the denominator, and nothing in the index detects it.
  • The platelet count must be in × 10⁹/L (the same number as × 10³/µL). A count entered in cells/µL is 1,000 times too large and would produce an index 1,000 times too small, with no error, which is why values above 1000 are refused.
  • Performance figures from different cohorts are not competing estimates of one property: the HIV/HCV derivation (AUROC 0.765, Ishak 4–6), HCV mono-infection (0.85, METAVIR F3–F4) and NAFLD (0.802, NASH CRN 3–4) differ in spectrum, prevalence, endpoint and reference standard.
  • Historical derivation cut-offs, not used for the bands on this page: Sterling 2006 derived FIB-4 in HIV/HCV co-infection with cut-offs of 1.45 and 3.25 against Ishak stage 4–6 on biopsy, later validated at the same values against METAVIR F3–F4 in HCV mono-infection (Vallet-Pichard 2007). They belong to a different population and endpoint and must not be read against this page’s bands.

Risk factors the score does not count:

  • Bilirubin, albumin and INR are not used, and the index carries no information on hepatic synthetic function or decompensation; it is not a severity measure.
  • Imaging and elastography are not part of the index.
  • The cause of an abnormal platelet count is not captured.

What the guidelines say

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AASLD 2023

The AASLD practice guidance uses FIB-4 as a first-line non-invasive test in metabolic liver disease and states that it has low accuracy below age 35.

View guideline source ↗
AGA 2021

The AGA clinical care pathway states that a FIB-4 below 1.3 can reliably exclude advanced fibrosis, with a lower cut-off of 2.0 in those older than 65.

View guideline source ↗
EASL–EASD–EASO 2024

The joint European guideline includes FIB-4 among non-invasive tests and reports thresholds for significant fibrosis (F2) and for cirrhosis separately from the advanced-fibrosis pair.

View guideline source ↗
ADA 2026

The ADA Standards of Care reference FIB-4 in adults with type 2 diabetes and note that it has not been validated below age 35.

View guideline source ↗
NICE NG49

NICE guideline NG49, updated 31 July 2026, does not include FIB-4; it uses the enhanced liver fibrosis (ELF) test at a threshold of 10.51 instead.

View guideline source ↗

Guideline positions are stated as published. Curie.MD Calc does not publish treatment direction.

Where this comes from

17

What was observed

< 1.30 (< 2.00 at age ≥65)Advanced fibrosis unlikelyNPV 90%, sensitivity 74% (NAFLD, n=541) · Shah 2009 cohort
1.30–2.67 inclusive (2.00–2.67 at age ≥65)IndeterminateAbout 30% of patients fall here (163/541) · Shah 2009 cohort
> 2.67Advanced fibrosis more likelyPPV 80%, specificity 98%, sensitivity 33% (NAFLD, n=541) · Shah 2009 cohort

References

  • 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. View source ↗
  • 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. View source ↗
  • 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. View source ↗
  • Sung S, et al. Age-dependent differences in FIB-4 predictions of fibrosis in patients with MASLD referred from primary care. Hepatol Commun. 2024;9(1):e0609. View source ↗
  • Moctezuma-Velázquez et al. 2024. PMC11634560. View source ↗
  • Vallet-Pichard A, Mallet V, Nalpas B, et al. FIB-4: an inexpensive and accurate marker of fibrosis in HCV infection. Comparison with liver biopsy and FibroTest. Hepatology. 2007;46(1):32-36. View source ↗
  • Mofrad P, Contos MJ, Haque M, et al. Clinical and histologic spectrum of nonalcoholic fatty liver disease associated with normal ALT values. Hepatology. 2003;37(6):1286-1292. View source ↗
  • Xiao et al. J Gen Intern Med. 2025. PMID 39060786. View source ↗
  • Mahady SE, Macaskill P, Craig JC, et al. Diagnostic accuracy of noninvasive fibrosis scores in a population of individuals with a low prevalence of fibrosis. Clin Gastroenterol Hepatol. 2017;15(9):1453-1460. View source ↗
  • Singh A, et al. J Clin Gastroenterol. 2020;54(10):891-897. View source ↗
  • Kim RG, et al. Diabetes Care. 2022;45(10):2449-2451. View source ↗
  • Green V, et al. J Clin Gastroenterol. 2024;58(8):825-829. View source ↗
  • 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. View source ↗
  • Kanwal F, Shubrook JH, Adams LA, et al. Clinical care pathway for the risk stratification and management of patients with nonalcoholic fatty liver disease. Gastroenterology. 2021;161(5):1657-1669. View source ↗
  • European Association for the Study of the Liver (EASL), European Association for the Study of Diabetes (EASD), European Association for the Study of Obesity (EASO). EASL-EASD-EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). J Hepatol. 2024;81(3):492-542. View source ↗
  • American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes—2026, Section 4: Comprehensive medical evaluation and assessment of comorbidities. Diabetes Care. 2026. View source ↗
  • National Institute for Health and Care Excellence. Non-alcoholic fatty liver disease (NAFLD): assessment and management. NICE guideline NG49 (updated 31 July 2026). View source ↗
Live result
FIB-4
0 of 4 answeredAnswer the remaining 4 to see the score
This is a screening index for advanced hepatic fibrosis, not a fibrosis stage and not a diagnosis. A result below the lower threshold makes advanced fibrosis unlikely; a result above the upper threshold makes it more likely but has a sensitivity of only about a third; a result between them is uninformative, which happens in roughly 30% of patients. Below age 35 no validated cut-off exists, so no band is given. A normal ALT does not exclude advanced fibrosis. It does not replace a reference-standard assessment and does not by itself determine referral.
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Curie.MD Calc is a reference and documentation tool for qualified healthcare professionals. It does not diagnose or recommend treatment; all results must be independently verified by the treating clinician. Not for use by patients.