Fibrosis-4 (FIB-4) Index for Liver Fibrosis

FIB-4 Index Calculator

Age

years

AST

U/L

ALT

U/L

Platelets

×10⁹/L

Noninvasive estimate of liver scarring in HCV and HBV patients, to assess need for biopsy.

Why Use

While liver biopsy is the gold standard for the diagnosis of liver fibrosis, it is not ideal; biopsy only evaluates a minute portion of the liver itself, so sampling errors can occur. Liver biopsy also comes with substantial morbidity. Liver fibrosis often progresses non-linearly, so it is important to be able to re-assess fibrosis trends in individual patients over time. It is critical that tests to identify liver cirrhosis are highly sensitive, as patients with the disease require screening for hepatocellular carcinoma (HCC) and gastroesophageal varices. The FIB-4 Index was shown to be superior to 7 other noninvasive markers of fibrosis in patients with NAFLD, including the NAFLD Fibrosis Score ( Shah 2009 ).

When to Use

Patients with any known risk factors for liver disease, including chronic hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease (NAFLD) and the cholestatic and metabolic liver diseases. Patients with known liver fibrosis should have their fibrosis trended over time to evaluate for progression or stabilization.

Formula

FIB-4 Score = (Age* x AST) / (Platelets x √(ALT)) *Use with caution in patients <35 or >65 years old, as the score has been shown to be less reliable in these patients.

Pearls / Pitfalls

Liver fibrosis often progresses non-linearly, so it is important to be able to re-assess fibrosis trends in individual patients over time, and invasive re-assessments carry significant risk to patients. FIB-4 allows for non-invasive liver fibrosis assessment. FIB-4 was developed in patients with HIV and HCV co-infection. FIB-4 was developed to correlate with Ishak levels of fibrosis (by biopsy) with 3 levels: 0-2 (mild fibrosis) 3-4 (moderate fibrosis) 5-6 (severe fibrosis/cirrhosis)

Advice

Low fibrosis scores may be appropriate candidates for medical management and may not require liver biopsy if FIB-4 scores continue to stay low. Severe fibrosis/cirrhosis scores may need liver biopsy for confirmation of cirrhosis unless there are other clinical or imaging signs of progression to end-stage liver disease.

More Information

Interpretation: *"Advanced fibrosis" was defined as METAVIR stage F3-F4 ( McPherson 2017 ). FIB-4 Score Approximate fibrosis stage* <1.45 0-1 1.45-3.25 2-3 >3.25 4-6 *Based on Ishak fibrosis staging ( Sterling et al 2006 ).