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The FIB-4 Score calculator computes the Fibrosis-4 score to measure the amount of scarring in a liver based on the patient's age, AST and ALT levels, and platelet count.
INSTRUCTIONS: Enter the following:
- (A) Age of Patient
- (AST) Aspartate Transaminase Level
- (PC) Platelet Count (billions per liter)
- (ALT) Alanine Transaminase Level
Fibrosis-4 Score (FIB-4): The calculator returns the score as a real number.
The Math / Science
The formula for FIB-4 is:
`"FIB-4" = (A * AST)/(PC * sqrt(ALT))`
where:
- FIB-4 = Fibrosis-4 Score
- A = Age of Patient in Years
- AST = Aspartate Transaminase enzyme level in units per liter
- PC = Platelet Count (billions per liter)
- ALT = Alanine Transaminase enzyme level in units per liter
Using This Score
Using a lower cutoff value of 1.45, a FIB-4 score <1.45 had a negative predictive value of 90% for advanced fibrosis (Ishak fibrosis score 4-6 which includes early bridging fibrosis to cirrhosis). In contrast, a FIB-4 >3.25 would have a 97% specificity and a positive predictive value of 65% for advanced fibrosis. In the patient cohort in which this formula was first validated, at least 70% patients had values <1.45 or >3.25. Authors argued that these individuals could potentially have avoided liver biopsy with an overall accuracy of 86%.
Sources
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.
