FIB-4 Index

FIB-4 Index

What it measures: fibrosis

Who should take it: anyone concerned about their liver

Where to get it: primary care provider, online calculator

The FIB-4 Index is a blood-based diagnostic test that looks at underlying fibrosis that can be used as a measure to help determine NAFLD/NASH status. While originally developed to detect liver fibrosis among patients with Hepatitis C and HIV, FIB-4 scoring has been increasingly used by the diabetes and NAFLD/NASH communities.[1] [2] [3] The FIB-4 scoring system is determined from the values of patient age, platelet count, aspartate aminotransferase (AST), and alanine aminotransferase (ALT).

fib4_calculation.png

As all of these tests are available to primary care physicians, FIB-4 is a highly accessible and affordable screening tool. A sample report can be seen below:

In clinical trials for NAFLD/NASH diagnosis, patients with a FIB-4 score <1.3 were classified as not having advanced fibrosis, while patients with a FIB-4 score >2.67 were classified as having advanced fibrosis.[4] Those with FIB-4 scores 1.3-2.6 were indeterminate, requiring further testing. As a test to rule out advanced fibrosis (FIB-4 <1.3), FIB-4 has a negative predictive value of 90-95%. This means that 90-95% of those identified as not having advanced fibrosis truly do not have advanced fibrosis, while the remaining 5-10% are false negatives requiring further validation. As a test to rule in advanced fibrosis (FIB-4 >2.6), FIB-4 has a positive predictive value of 80%. This means that 80% of those identified as having advanced fibrosis truly have advanced fibrosis, while the remaining 20% are false positives requiring further validation.

Unlike some other tests, FIB-4 looks solely at fibrosis, not taking into consideration other factors important for diagnosis and monitoring of NAFLD/NASH such as steatosis and activity. While it is fairly limited in this sense, the high accuracy in detection of fibrosis makes it a strong starting point for NAFLD/NASH diagnosis that can help the right patients get on track for further testing and treatment. As all of these tests are readily available to primary care physicians, FIB-4 is a highly accessible and affordable screening tool. If you have your platelet count, AST, and ALT values from a previous bloodwork, you can enter them yourself in the calculator here:

CLICK HERE TO LINK TO FIB-4 CALCULATOR PAGE

 

[1] Sterling et al., Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection, Hepatology, June 2006, doi: 10.1002/hep.21178.

[2] Filozof et al., Liver Fibrosis as Assessed by the FIB-4 Index in Patients with Type 2 Diabetes (T2DM), Diabetes, July 2018, doi: 10.2337/db18-1570-P.

[3] Shah et al., USE OF THE FIB4 INDEX FOR NON-INVASIVE EVALUATION OF FIBROSIS IN NONALCHOLIC FATTY LIVER DISEASE, Clinical Gastroenterology and Hepatology, October 2009, doi: 10.1016/j.cgh.2009.05.033.

[4] Alkhouri and McCullough, Noninvasive Diagnostics of NASH and Liver Fibrosis Within the Spectrum of NAFLD, Gastroenterology & Hepatology, October 2012.

 


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