FIB-4 Calculator

To use our F4 fibrosis tool, you'll need to prepare the following blood tests results:

• AST - usually given in U/L (also called: aspartate transaminase/ AspAT/ ASAT/ AAT/ GOT/ SGOT);
• ALT - usually given in U/L (alanine transaminase / alanine aminotransferase/ ALAT/ SGPT); and
• Platelet count - you can find either the number of platelets per mm³, the number of platelets per μL, or the number of platelets × 10⁹ per liter.

Remember, our FIB-4 calculator works best for people aged 35-65 years old.
People outside of this bracket may receive a false-positive result.

💡 False positive - a situation where a healthy person receives a result that strongly suggests that they are sick.

FIB-4 is used mostly for people with NAFLD (read below), and HCV, HBV, or HIV co-infections. It is a non-invasive fibrosis and subsequent loss of liver function assessment.

• FIB-4 > 3.25 - should confirm the presence of advanced fibrosis (F3-F4) in 82.1% of patients; and
• FIB-4 < 1.45 - should exclude the presence of advanced fibrosis (F3-F4) in 94.7% of patients. (read more in article by Vallet-Pichard et al.)

NAFLD is an abbreviation for Non-Alcoholic Fatty Liver Disease. NAFLD is the most common liver disease worldwide - it's a condition that, may, over time, lead to an irreversible cirrhosis of the liver, and a permanent loss of liver function. In comparison to NASH (Non-Alcoholic SteatoHepatitis), NAFLD does not consist of liver inflammation. The reasons NAFLD and NASH develop include:

• Obesity;
• Metabolic syndrome (connected with obesity, includes, for example, hypertension or type 2 diabetes);
• Drugs, toxins; and
• Inherited metabolic diseases.

Liver damage, such as cirrhosis or inflamation, is also caused by the chronic intake of too many units of alcohol. The Audit-C score may be helpful in screening those potentially at risk.

Don't hesitate to ask for professional help if you think you may need it.

The NAFLD fibrosis score can be presented in a single equation:

FIB-4 = (age × AST) / ( platelet count × √ALT)

Note, that the *ALT levels need to be square rooted!

The APRI ratio is a simple way to assess the probability of fibrosis progression among patients suffering from hepatitis type C.

The APRI formula is as follows:

APRI = (AST / upper limit of normal AST) / platelet count

*Most experts suggest using the value of 40 U/L as the upper normal AST level limit - we also decided to use this value in our calculator.

Interpretation:

A value of ≥1 means that there is a high possibility of severe cirrhosis. In general, a high APRI value indicates an increased risk of disease progression.

A value <0.5 can rule out the possibility of progression in around 87% of cases.

Apart from the FIB-4 or APRI score, we use plenty of different fibrosis scores to asses the probability of the liver disease, with varying levels of invasivity. Let's enumerate a few of them:

• The AST/ALT ratio;
• The albumin gradient in ascites;
• The FibroTest; and
• A liver biopsy - the most invasive method.