FIB-4 for fatty liver
Rules advanced fibrosis (F3–F4) in or out in MASLD/NAFLD from four routine values, as the first step before elastography. Everything is calculated on your device; nothing you type is sent or stored.
Enter age, AST, ALT and platelets.
How do I read the result?
| FIB-4 | Advanced fibrosis | Next step |
|---|---|---|
| Below 1.30 below 2.0 from 65 years | Unlikely (rules out) | Manage metabolic risk factors in primary care; re-assess every 1–3 years. |
| 1.30 – 2.67 2.0 – 2.67 from 65 years | Grey zone | Liver stiffness by transient elastography (FibroScan); INASL places it at tertiary level, so refer. EASL also allows a year of lifestyle and cardiometabolic treatment, then a repeat FIB-4. |
| Above 2.67 | Likely (rules in) | Refer to a hepatologist / gastroenterologist for elastography and staging. |
In the NAFLD cohort that set these cut-offs (541 adults with biopsy), FIB-4 of 1.30 or less had a 90% negative predictive value and 2.67 or more an 80% positive predictive value for advanced fibrosis; AUROC 0.80. The low cut-off is there to keep most patients out of the elastography queue safely; the price is a grey zone between the two cut-offs, where a second test decides.
What liver stiffness confirms it?
| Liver stiffness (VCTE) | INASL 2023 | EASL 2024 |
|---|---|---|
| Significant fibrosis (F2 or more) | 8.2 kPa or more; under 6.0 makes it unlikely | — |
| Advanced fibrosis (F3 or more) | 9.7 kPa or more | below 8 rules out, 12 or more rules in |
| Cirrhosis (F4) | 13.6 kPa or more | — |
INASL takes significant fibrosis (F2 or more), not F3, as the entry point for referral. In Indian data it quotes FIB-4 below 1 as ruling out significant fibrosis with very high sensitivity.
Who should have it?
INASL suggests looking for fatty liver in people with type 2 diabetes, obesity or metabolic syndrome, and recommends FIB-4 (or APRI) as the first fibrosis test at primary and secondary care. EASL adds abnormal liver tests. Normal ALT does not exclude advanced fibrosis.
When is it misleading?
- Under 35: the index performs poorly (AUROC about 0.60); a low value is not reassuring.
- 65 and over: age alone pushes FIB-4 up, so specificity with 1.30 falls to about 35%; the 2.0 cut-off brings it to about 70% (McPherson 2017; used by EASL 2024, not stated by INASL).
- AST or ALT not from the liver's chronic state: acute hepatitis, a recent alcohol binge, heavy exercise or muscle injury, haemolysis.
- Platelets low for another reason: ITP, marrow disease, hypersplenism from non-cirrhotic portal hypertension; or high after splenectomy.
- Other liver diseases: the 1.30 / 2.67 cut-offs are for fatty liver. In hepatitis C and HIV co-infection, where FIB-4 was first built, the cut-offs were 1.45 and 3.25.
Common questions
What is the FIB-4 formula?
FIB-4 = (age in years × AST in U/L) ÷ (platelets in 10⁹/L × √ALT in U/L). Platelets reported as 2.5 lakh/mm³ are 250 × 10⁹/L.
What FIB-4 cut-offs are used in fatty liver?
INASL (2023) uses below 1.3 to rule out advanced fibrosis (F3–F4), 1.3 to 2.67 as the grey zone and above 2.67 to rule it in, the same as EASL-EASD-EASO (2024). In the NAFLD study that set them, 1.30 or less had a negative predictive value of 90% and 2.67 or more a positive predictive value of 80%. From 65 years a lower cut-off of 2.0 is used (McPherson 2017, EASL 2024); INASL gives no age-specific cut-off.
Why not use the 1.45 and 3.25 cut-offs?
Those were derived in HIV/hepatitis C co-infection (Sterling 2006). In NAFLD/MASLD the validated cut-offs are 1.30 and 2.67 (Shah 2009), which INASL and EASL-EASD-EASO use.
When is FIB-4 unreliable?
Under 35 years (it performs poorly), and when AST, ALT or platelets are moved by something other than chronic liver fibrosis: acute hepatitis or a recent alcohol binge, muscle injury, haematological causes of a low platelet count, or splenectomy.
Sources
- Sterling RK, et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology 2006;43:1317-25.
- Shah AG, et al. Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol 2009;7:1104-12.
- McPherson S, et al. Age as a confounding factor for the accurate non-invasive diagnosis of advanced NAFLD fibrosis. Am J Gastroenterol 2017;112:740-51.
- Duseja A, et al. Indian National Association for Study of the Liver (INASL) guidance paper on nomenclature, diagnosis and treatment of nonalcoholic fatty liver disease (NAFLD). J Clin Exp Hepatol 2023;13:273-302.
- EASL-EASD-EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). J Hepatol 2024;81:492-542.