1FIB-4 Score Interpretation
The following cutoffs apply to adults with known or suspected chronic liver disease (HCV, HBV, NAFLD/MASLD). Scores in the indeterminate range (1.30–2.67) require additional investigation.
| FIB-4 Score | Risk Category | Fibrosis Stage | NPV / PPV | Clinical Action |
|---|---|---|---|---|
| < 1.30 | 🟢 Low Risk | F0–F1 (Mild) | NPV ~90% | Biopsy can be deferred. Monitor annually with LFTs + repeat FIB-4. |
| 1.30–2.67 | 🔵 Indeterminate | F1–F3 (Variable) | — | Additional testing needed — FibroScan, NAFLD Fibrosis Score, APRI, or liver biopsy. |
| > 2.67 | 🔴 High Risk | F3–F4 (Advanced) | PPV ~65% | Refer to hepatologist. Consider biopsy to confirm cirrhosis; HCC surveillance if cirrhosis. |
⚠️ Age Caveat (important in Indian practice)
FIB-4 is less reliable in patients aged <35 years (may underestimate fibrosis) and >65 years (may overestimate due to age-related thrombocytopenia). For older patients, some authorities use a modified low-risk cutoff of <2.0 instead of <1.30.
2Formula & Variables
FIB-4 = ( Age [yr] × AST [U/L] ) ÷ ( Platelets [10⁹/L] × √ALT [U/L] )
// Variables:
Age → Patient age in years
AST → Aspartate aminotransferase (U/L)
ALT → Alanine aminotransferase (U/L)
Platelets → Platelet count (×10⁹/L; i.e. thousands/µL)
// Cutoffs (validated): Low <1.30 · Indeterminate 1.30–2.67 · High >2.67
All four variables are available from a routine complete blood count (CBC) and liver function test (LFT) panel — no additional tests are required. Enter AST and ALT in U/L (not IU/L — they are equivalent). Platelet count must be in ×10⁹/L (same as 10³/µL or thousands/µL as reported in most Indian lab reports).
3What Is the FIB-4 Index?
The FIB-4 (Fibrosis-4) Index is a validated, non-invasive scoring system that estimates the degree of liver fibrosis without the need for a liver biopsy. Originally developed in 2006 by Sterling et al. for HIV/HCV co-infected patients, it has since been validated extensively for:
- Chronic Hepatitis C (HCV)
- Chronic Hepatitis B (HBV)
- NAFLD / MASLD (Metabolic dysfunction-Associated Steatotic Liver Disease)
- Alcoholic liver disease
- Post-treatment response monitoring in HCV after direct-acting antivirals (DAAs)
FIB-4 combines four routinely available parameters — Age, AST, ALT, and Platelet count — into a single number that correlates with hepatic fibrosis stage on liver biopsy (METAVIR scale F0–F4). It is endorsed by the AASLD, EASL, and increasingly by Indian hepatology practice guidelines.
Why FIB-4 Matters in India
India bears a significant burden of chronic liver disease, with HBV affecting an estimated 40 million and HCV affecting 6–12 million individuals. MASLD prevalence is rising with the epidemic of obesity and type 2 diabetes. Liver biopsy — the traditional gold standard for fibrosis staging — is invasive, costly, subject to sampling error, and impractical for population-level screening. FIB-4 provides an accessible, cost-effective first-line fibrosis assessment that can be calculated from a standard CBC and LFT — tests already ordered in most outpatient and inpatient encounters.
4When to Use FIB-4
- Initial fibrosis assessment in newly diagnosed HCV, HBV
- Screening for advanced fibrosis in NAFLD/MASLD before FibroScan
- Post-DAA SVR monitoring in HCV
- Risk stratification in primary care before hepatology referral
- Avoiding unnecessary liver biopsy in low-risk patients (<1.30)
- Age <35 or >65 years (unreliable; use with caution)
- Acute hepatitis (AST/ALT spuriously high)
- Immune thrombocytopenia or other causes of low platelets unrelated to portal hypertension
- Haemolysis (falsely elevated AST)
- Active myositis / strenuous exercise (elevated AST)
- Not validated for autoimmune hepatitis, PBC, PSC
5FIB-4 in NAFLD / MASLD
MASLD (formerly NAFLD) has emerged as the most common chronic liver disease globally, affecting ~25–38% of adults in India. Identifying patients with significant fibrosis (F≥2) is critical because advanced fibrosis — not steatosis or NASH activity — is the primary driver of liver-related mortality in MASLD.
The AASLD 2023 and EASL 2024 MASLD guidelines recommend using FIB-4 as the initial non-invasive test in all patients with suspected MASLD:
- FIB-4 <1.30: Reassure patient; manage metabolic risk factors; repeat FIB-4 in 1–2 years.
- FIB-4 1.30–2.67: Indeterminate — proceed to vibration-controlled transient elastography (FibroScan) or ELF (Enhanced Liver Fibrosis) test.
- FIB-4 >2.67: High likelihood of advanced fibrosis — refer to hepatologist for further workup and HCC surveillance consideration.
FIB-4 performs slightly less well in MASLD than in viral hepatitis (AUROCs of 0.76–0.82 for F≥3 detection), partly because metabolic inflammation causes AST/ALT elevation that may inflate the score independently of fibrosis. However, it remains the most practical initial gating tool.
6FIB-4 vs Other Non-Invasive Tests
| Test | Variables | Best Used For | Availability in India |
|---|---|---|---|
| FIB-4 | Age, AST, ALT, Platelets | HCV, HBV, NAFLD — initial screen | ✅ Free (routine labs) |
| APRI | AST, Platelets | HCV — WHO-endorsed in low-resource settings | ✅ Free (2 parameters) |
| NAFLD Fibrosis Score | Age, BMI, IFG, AST, ALT, Platelets, Albumin | NAFLD/MASLD — more variables, higher accuracy | ✅ Free (calculated) |
| FibroScan (LSM) | Liver stiffness (kPa) | All chronic liver diseases — gold standard non-invasive | ⚠️ Tertiary centres; ₹3,000–8,000 |
| ELF Test | HA, PIIINP, TIMP-1 | MASLD — regulatory approved | ❌ Rarely available in India |
| Liver Biopsy | Histology | Gold standard — confirms stage | ⚠️ Available; invasive; ₹5,000–20,000+ |
7Clinical Workflow: How to Use This Score
- Order baseline labs — CBC (for platelet count) + LFT (AST, ALT) if not already available. These are available in any NABL-accredited lab at ₹200–500.
- Enter values into this calculator and note the FIB-4 score.
- If FIB-4 <1.30: Reassure patient; address underlying cause (antiviral therapy for HCV/HBV, metabolic management for MASLD); repeat FIB-4 in 12 months.
- If FIB-4 1.30–2.67: Refer for FibroScan (if available) or hepatology consultation. Consider NAFLD Fibrosis Score as complementary tool.
- If FIB-4 >2.67: High priority hepatology referral. Discuss liver biopsy vs. elastography. Begin HCC surveillance (6-monthly USG abdomen ± AFP) if cirrhosis is confirmed or strongly suspected.
For HCV patients post-SVR: FIB-4 improves significantly after sustained virological response (SVR) with DAAs but may remain elevated if cirrhosis was already established. A FIB-4 >2.0 at 12 weeks post-SVR warrants continued HCC surveillance regardless of symptom resolution.
8Frequently Asked Questions
The FIB-4 index uses routine age, liver enzymes, and platelet count to non-invasively stratify liver fibrosis risk in HCV, HBV, and NAFLD/MASLD, helping defer unnecessary biopsies in low-risk patients.