Question 1

What is the FIB-4 index?

Accepted Answer

FIB-4 is a noninvasive score that combines age, AST, ALT, and platelet count to estimate the likelihood of advanced liver fibrosis. It was originally developed and validated in patients with HIV/hepatitis C coinfection and is now widely used more broadly, including in fatty liver disease (NAFLD/MASLD) screening.

Question 2

How do I interpret my FIB-4 score?

Accepted Answer

A score below 1.45 suggests a low probability of advanced fibrosis, above 3.25 suggests a high probability, and scores in between are indeterminate and generally call for further testing (such as elastography or specialist referral) rather than a conclusion either way.

Question 3

Is FIB-4 reliable in older adults?

Accepted Answer

FIB-4 tends to run higher with age even without more fibrosis, which increases false positives in people over 65. Some guidelines suggest a higher low-risk cutoff (around 2.0) in that age group. This calculator uses the standard 1.45/3.25 cutoffs; discuss age-adjusted interpretation with a clinician if relevant.

Question 4

Can FIB-4 replace a liver biopsy?

Accepted Answer

No. FIB-4 is a screening tool meant to help prioritize who needs further evaluation, not a diagnostic replacement for biopsy or advanced imaging like elastography (FibroScan), which remain more accurate for staging fibrosis directly.

Question 5

What labs do I need for this calculator?

Accepted Answer

A basic metabolic panel isn’t enough — you need AST and ALT (from a liver panel) plus a platelet count (from a complete blood count), typically drawn together as part of routine liver disease workup.

FIB-4	Interpretation
< 1.45	Low probability of advanced fibrosis
1.45–3.25	Indeterminate
> 3.25	High probability of advanced fibrosis

FIB-4 Index Calculator

How FIB-4 is calculated

Interpreting the score

Common questions