Fibrosis 4 (FIB 4) Score

Evaluates liver fibrosis based on age, platelet count, AST and ALT to help with cirrhosis diagnosis.

In the text below the calculator there is more information on the score and on the study it originated from.

The FIB 4 score is a non-invasive liver fibrosis assessment based on patient age, platelet count, AST and ALT values.

Because this type of fibrosis progresses non-linearly, regular evaluation is important to trace its progression.

This can be done through invasive procedures such as liver biopsy but these carry a high risk of complications.

FIB 4 score = (Age x AST) / (Platelet count x (square root of ALT))

There are three types of results:

■ FIB 4 <1.45: absence of cirrhosis;

■ FIB 4 between 1.45 - 3.25: inconclusive;

■ FIB 4 >3.25: cirrhosis.

Patients with low scores do not generally require liver biopsy. Patients with high scores usually undergo biopsy to confirm or rule out cirrhosis diagnosis.

Patient age
Platelet Count (109/L)
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FIB 4 formula

The FIB 4 score evaluates the degree of fibrosis in patients suspected of or already diagnosed with hepatic fibrosis.

The score contributes to assessment of NASH (non-alcoholic steatohepatitis), HCV (hepatic C virus) or cholestatic and metabolic liver diseases.

There are four variables taken into account:

■ Patient age is used because there is a direct correlation between age increase and progression of liver fibrosis. This is particularly obvious in patients with hepatitis C and chronic alcohol consumption.

■ AST is aspartate aminotransferase which is an enzyme found in several types of tissue (liver, kidney, heart, brain). Normal values are between 5 and 40 IU/L and increases usually suggest tissue injury.

■ ALT is the alanine aminotransferase which is an enzyme specific to hepatic tissue that also shows injury when higher than 7-56 IU/L.

■ Platelet count is used to identify whether there are sufficient clotting particles (those produced by liver) and thus indirectly test liver function.

This score employs the following equation:

FIB 4 = (Age x AST) / (Platelet count x √ALT)

It can help with regular assessment of fibrosis without the need for carrying a highly invasive procedure with substantial morbidity, such as liver biopsy.


Score interpretation

The result provided from the above equation is interpreted according to two cut off values:

■ FIB 4 <1.45 indicates absence of cirrhosis (with a negative predictive value of 90% for advanced fibrosis);

■ FIB 4 between 1.45 - 3.25 are deemed inconclusive;

■ FIB 4 >3.25 indicates cirrhosis (with a positive predictive value of 65% for advanced fibrosis).

Patients with low score are not required to undergo liver biopsy (as medical management is sufficient) but patients with high scores may be, as to confirm or infirm liver disease diagnosis.

Where a patient scores high and also has other clinical or imaging signs of progression to end-stage liver disease, biopsy may not be necessary anymore.

Also, patient with liver cirrhosis often need to undergo screening for hepatocellular carcinoma (HCC) and gastroesophageal varices.


About the study

This non-invasive fibrosis score was created by Sterling et al. in 2006 and was aimed at patients with HIV/hepatitis C virus coinfection.

A retrospective analysis was performed in 832 patients (design and validation set) and the liver fibrosis was evaluated via Ishak score. Multivariate logistic regression analysis revealed the four parameters most significantly associated with fibrosis.

It was found that by using the FIB 4, 87% of the 198 patients with FIB-4 values outside 1.45-3.25 (the inconclusive interval) would be correctly classified. This meant an avoidance of unnecessary liver biopsy in 71% of the validation group.


Liver fibrosis causes

The hepatic tissue scars as a result of injury, be it caused by disease or trauma. This is the process in which the tissue regenerates by depositing new collagen.

Unfortunately, this comes at a price for normal liver units and the overall hepatic function is impaired at different degrees.

When fibrosis is extended, cirrhosis installs and this can lead up to liver failure.

The main two diseases that cause fibrosis of the liver are chronic viral hepatitis B and alcoholic liver disease. Other conditions are non-alcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC).

Nonalcoholic steatohepatitis or NASH is the most severe type of NAFLD and occurs when liver function is impaired by fatty deposits, inflammation and fibrosis.


Original source

Sterling RK, Lissen E, Clumeck N, et. al. Development of a simple noninvasive index to predict significant fibrosis patients with HIV/HCV co-infection. Hepatology 2006; 43:1317-1325.


Kim BK, Kim DY, Park JY, Ahn SH, Chon CY, Kim JK, Paik YH, Lee KS, Park YN, Han KH. Validation of FIB-4 and comparison with other simple noninvasive indices for predicting liver fibrosis and cirrhosis in hepatitis B virus-infected patients. Liver Int. 2010; 30(4):546-53.

Other references

1. Vallet-Pichard A, Mallet V, Nalpas B, Verkarre V, Nalpas A, Dhalluin-Venier V, Fontaine H, Pol S. FIB-4: an inexpensive and accurate marker of fibrosis in HCV infection. comparison with liver biopsy and fibrotest. Hepatology. 2007; 46(1):32-6.

2. Martínez SM, Crespo G, Navasa M, Forns X. Noninvasive assessment of liver fibrosis. Hepatology. 2011; 53(1):325-35.

Specialty: Hepatology

System: Digestive

Objective: Evaluation

Type: Score

No. Of Variables: 4

Year Of Study: 2006

Abbreviation: FIB 4

Article By: Denise Nedea

Published On: May 31, 2017

Last Checked: May 31, 2017

Next Review: May 31, 2023