Non-invasive liver fibrosis staging using Age, AST, ALT & Platelet count — validated for HCV, HBV, and NAFLD/MASLD. Instant F-stage interpretation with biopsy guidance.
Normal: 150–400 ×10⁹/L
Aspartate aminotransferase · Normal: 10–40 U/L
Alanine aminotransferase · Normal: 7–56 U/L
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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.
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).
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:
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 (American Association for Study of Liver Diseases), EASL (European Association for the Study of the Liver), and increasingly by Indian hepatology practice guidelines.
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.
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 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.
| Test | Variables | Best Used For | Availability in India |
|---|---|---|---|
| FIB-4 | Age, AST, ALT, Platelets | HCV, HBV, NAFLD — initial screen | ✅ Free (calculated from routine labs) |
| APRI | AST, Platelets | HCV — WHO-endorsed in low-resource settings | ✅ Free (2 routine 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+ |
📋 Suggested Approach for Primary Care (India)
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.
The FIB-4 (Fibrosis-4) Index is a non-invasive scoring system that estimates the degree of liver fibrosis using four readily available blood test parameters: Age, AST (aspartate aminotransferase), ALT (alanine aminotransferase), and Platelet count. It was originally validated for HIV/HCV co-infected patients and is now widely used for HCV, HBV, and NAFLD/MASLD.
FIB-4 = (Age [years] × AST [U/L]) ÷ (Platelet count [10⁹/L] × √ALT [U/L])
All four parameters come from routine blood tests — no liver biopsy needed. Note that platelet count must be entered in ×10⁹/L (equivalent to thousands per µL or 10³/µL, as typically reported in Indian labs).
FIB-4 < 1.30 (Low Risk): Advanced fibrosis is unlikely — corresponds to METAVIR F0–F1. The negative predictive value (NPV) is approximately 90% for ruling out F3–F4 fibrosis. Biopsy can usually be deferred.
FIB-4 1.30–2.67 (Indeterminate): Results are inconclusive in this range. Additional testing such as FibroScan (transient elastography), the NAFLD Fibrosis Score, ELF test, or liver biopsy is recommended.
FIB-4 > 2.67 (High Risk): Advanced fibrosis (F3–F4) or cirrhosis is likely. The positive predictive value (PPV) is approximately 65%. Hepatology referral and further evaluation are recommended.
A FIB-4 score below 1.30 is considered within the low-risk range, suggesting minimal or no significant liver fibrosis (METAVIR F0–F1). However, "normal" is context-dependent — in patients aged >65 years, some guidelines suggest using <2.0 as the low-risk threshold due to the tendency for the score to be elevated with advancing age even without significant fibrosis.
FIB-4 cannot fully replace liver biopsy but can significantly reduce the need for it. Patients with clearly low (<1.30) or clearly high (>2.67) scores can often be managed without biopsy. Those in the indeterminate zone (1.30–2.67) may still need biopsy or complementary non-invasive tests like FibroScan. Always interpret in the context of clinical history, imaging, and other lab findings.
Yes. FIB-4 is increasingly used for NAFLD (now classified as MASLD — Metabolic dysfunction-Associated Steatotic Liver Disease). The same cutoffs (1.30 and 2.67) apply. The EASL 2024 and AASLD 2023 MASLD guidelines endorse FIB-4 as an initial non-invasive test for fibrosis assessment before considering FibroScan or liver biopsy.
Age is a direct component of the FIB-4 numerator — it multiplies the score. In younger patients (<35 years), even with significant fibrosis, the low age value may produce a falsely low FIB-4. In older patients (>65 years), platelet counts tend to decline with age (age-related thrombocytopenia) independently of portal hypertension or fibrosis, which can falsely elevate the FIB-4 score. For patients >65 years, some authorities use a modified low-risk cutoff of <2.0 instead of <1.30.
Both are non-invasive fibrosis scores derived from routine labs. APRI (AST-to-Platelet Ratio Index) uses only AST and Platelet count (APRI = (AST/ULN of AST) × 100 / Platelets), while FIB-4 additionally incorporates Age and ALT. FIB-4 generally demonstrates better diagnostic accuracy, particularly for distinguishing advanced fibrosis (F3–F4) from mild fibrosis, and is more widely recommended in current AASLD and EASL guidelines. APRI remains relevant in resource-limited settings due to its simplicity (only 2 variables).
This calculator requires platelet count in ×10⁹/L (also written as 10³/µL or thousands/µL). Indian CBC reports commonly show platelets in lakh/µL or ×10⁵/µL — for example, "2.5 lakh/µL." To convert: multiply by 100 to get ×10⁹/L (so 2.5 lakh = 250 ×10⁹/L). Or simply use the absolute count in thousands: 2,50,000/µL = 250 ×10⁹/L.
In patients with stable low scores (<1.30) without active liver disease, annual reassessment is reasonable. In patients on treatment (e.g., HCV DAAs, MASLD lifestyle modification), repeat FIB-4 at 12–24 weeks post-intervention and at 12 months can monitor treatment response. In those with high or indeterminate scores under active hepatology follow-up, the timing is guided by the specialist. Note that FIB-4 can improve significantly after successful HCV treatment (SVR) but may remain elevated if cirrhosis is already established.