FIB-4 - non-invasive liver fibrosis assessment

FIB-4 (Fibrosis-4 Index) is a clinically validated calculation algorithm used for the non-invasive estimation of the probability of advanced liver fibrosis. It enables an initial assessment of liver fibrosis risk based on specific biological parameters determined in the laboratory.

The test is primarily recommended for adults with chronic liver diseases or risk factors for liver fibrosis, including individuals with metabolic dysfunction-associated steatotic liver disease (MASLD), type 2 diabetes mellitus, obesity, metabolic syndrome, or persistent abnormalities of liver function tests.

FIB-4 contributes to risk stratification and helps identify patients who may require additional investigations, such as liver elastography or other specialized fibrosis assessment methods.

Research method 

The investigation involves the collection of a venous blood sample and laboratory determination of the following parameters:

• AST (aspartate aminotransferase);
• ALT (alanine aminotransferase);
• platelet count.

The FIB-4 value is calculated automatically using a clinically validated algorithm that integrates these parameters together with the patient’s age.

Indications

• metabolic dysfunction-associated steatotic liver disease (MASLD) or suspected hepatic steatosis;
• type 2 diabetes mellitus;
• obesity or metabolic syndrome;
• elevated or persistent abnormalities of liver transaminases;
• hepatic steatosis detected by ultrasound or other imaging methods;
• chronic alcohol consumption or suspected alcohol-related liver disease;
• chronic viral hepatitis B, C, or D.

FIB-4 may also be used as a non-invasive initial assessment method for liver fibrosis risk in individuals with risk factors for liver injury.

Procedure

The investigation requires the collection of a venous blood sample. The required parameters are analyzed in the laboratory, and the FIB-4 value is calculated automatically based on the available data.

The result is reported as a numerical value and is accompanied by an indicative interpretation of the risk category for advanced liver fibrosis.

Limitations

The result should be interpreted in a clinical context, as FIB-4 values may be influenced by:

• acute hepatitis or transient increases in transaminase levels;
• non-hepatic thrombocytopenia;
• recent or chronic alcohol consumption;
• muscle disorders or intense physical exercise.

FIB-4 estimates the probability of advanced liver fibrosis but does not establish the diagnosis on its own. Intermediate- or high-risk results require medical interpretation and, when appropriate, additional investigations such as liver elastography or other fibrosis assessment methods.

Age-related interpretation considerations

Interpretation of the FIB-4 result may require adjustment depending on the patient’s age.

In patients aged ≥65 years, when interpreting FIB-4 in the context of MASLD, the use of an adjusted lower threshold of 2.0 is recommended.

In patients younger than 35 years, the diagnostic accuracy of the test is lower. In the presence of hepatic steatosis, elevated transaminase levels, or cardiometabolic risk factors, the assessment may be complemented by liver elastography or another validated non-invasive test.
 

Sources:

https://www.aasld.org/liver-fellow-network/core-series/clinical-pearls/spare-me-jab-noninvasive-assessment-patients-masld
https://pubmed.ncbi.nlm.nih.gov/38708469/
https://easl.eu/wp-content/uploads/2021/09/Non-alcoholic-fatty-liver-disease-A-patient-guideline-final.pdf