# What is my FIB-4 score?

Calculates the FIB-4 liver fibrosis index from age, AST, ALT, and platelet count (Sterling 2006) and reads it with the published cut-offs for fatty liver disease (MASLD) or for hepatitis C and HIV.

- Page: https://www.acalculator.org/health/fib-4-calculator
- JSON spec: https://www.acalculator.org/health/fib-4-calculator.json
- Version: dca4d7ad8725

## Default answer

Example with the default inputs (Liver condition Fatty liver (MASLD), Age 55, AST (U/L) 40, ALT (U/L) 35, Platelets (×10⁹/L) 210): The FIB-4 index is 1.77. Indeterminate: further testing is often needed.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| for | Liver condition | Which cut-offs to read the score with: fatty liver disease (MASLD or NAFLD), or hepatitis C and HIV. |
| age | Age | Age in whole years. |
| ast | AST (U/L) | Aspartate aminotransferase from the blood test, in units per liter. |
| alt | ALT (U/L) | Alanine aminotransferase from the blood test, in units per liter. |
| plt | Platelets (×10⁹/L) | Platelet count in 10⁹ per liter, the same number as 10³ per microliter. 210,000/µL is 210. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| fib4 | FIB-4 | The FIB-4 index, to 2 decimals. |
| reading | What the cut-offs say | How the published cut-offs for the chosen condition read the score. |
| cutoffs | Cut-offs used | The low and high cut-offs applied. |

## Method

FIB-4 = (age × AST) ÷ (platelets × √ALT), with AST and ALT in U/L and platelets in 10⁹/L.

## Assumptions

- The index is rounded to 2 decimals and read from the rounded value.
- MASLD: under 1.30 low (under 2.00 at age 65 or older), over 2.67 high (Shah 2009, McPherson 2017, AASLD 2023). Hepatitis C or HIV: under 1.45 low, over 3.25 high (Sterling 2006).
- FIB-4 is less accurate under age 35 and in acute hepatitis.

## Worked examples

1. for = masld, age = 55, ast = 40, alt = 35, plt = 210 gives fib4 = 1.77, reading = Indeterminate: further testing is often needed. Source: Sterling 2006: FIB-4 = (55 × 40) ÷ (210 × √35) = 1.7709, shown as 1.77; MASLD cut-offs 1.30 and 2.67 (Shah 2009).
2. for = masld, age = 45, ast = 25, alt = 30, plt = 250 gives fib4 = 0.82, reading = Low: advanced fibrosis is unlikely.
3. for = hcv, age = 62, ast = 90, alt = 60, plt = 110 gives fib4 = 6.55, reading = High: advanced fibrosis is likely. Source: (62 × 90) ÷ (110 × √60) = 6.5490, over 3.25 (Sterling 2006).
4. for = masld, age = 70, ast = 30, alt = 25, plt = 200 gives fib4 = 2.1, reading = Indeterminate: further testing is often needed, cutoffs = under 2.00 low, over 2.67 high.

## FAQ

### What is the FIB-4 score?

FIB-4 (fibrosis-4) is an index from four routine values: age, the liver enzymes AST and ALT, and the platelet count. Sterling and others built it in 2006 to estimate how much scarring (fibrosis) there is in the liver without a biopsy. It is best at ruling out advanced fibrosis.

### What is a normal FIB-4?

For fatty liver disease (MASLD, formerly NAFLD), a FIB-4 under 1.30 means advanced fibrosis is unlikely, and over 2.67 means it is likely (Shah 2009). From age 65, the low cut-off is 2.0, because FIB-4 rises with age (McPherson 2017). For hepatitis C or HIV, Sterling used under 1.45 and over 3.25.

### What happens with an indeterminate FIB-4?

A result between the two cut-offs cannot rule fibrosis in or out. The AASLD 2023 guidance on MASLD suggests a second test, such as liver stiffness by elastography or the ELF blood test. Your clinician decides what fits.

### Why does age matter?

Age is part of the formula, so the index rises with age even when the liver is the same. That makes the low cut-off less reliable in people 65 or older, and the index is not well studied under age 35.

### What units does FIB-4 use?

AST and ALT in units per liter (U/L), and platelets in 10⁹ per liter, which is the same number as thousands per microliter. A platelet count of 210,000/µL is 210.

## Sources

- 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. https://doi.org/10.1002/hep.21178
- 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. https://doi.org/10.1016/j.cgh.2009.05.033
- 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. https://doi.org/10.1038/ajg.2016.453
- 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. https://doi.org/10.1097/HEP.0000000000000323