NAFLD Fibrosis Score Calculator
Estimate advanced liver fibrosis likelihood from age, BMI, glycemic status, AST/ALT ratio, platelets, and albumin.
NAFLD fibrosis assessment
Enter contemporaneous clinical and laboratory values for an adult with suspected or established NAFLD.
About the NAFLD Fibrosis Score
The NAFLD Fibrosis Score (NFS) is a noninvasive clinical model developed to help estimate the likelihood of advanced fibrosis in adults with non-alcoholic fatty liver disease. It combines routinely available information rather than requiring an immediate liver biopsy. The six inputs are age, body mass index, impaired fasting glucose or diabetes status, the ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT), platelet count, and serum albumin. Together these variables reflect demographic, metabolic, hepatic, and hematologic patterns associated with fibrosis.
The published equation is NFS = -1.675 + 0.037 times age + 0.094 times BMI + 1.13 when impaired fasting glucose or diabetes is present + 0.99 times the AST/ALT ratio - 0.013 times platelet count - 0.66 times albumin. Age is entered in years, BMI in kg/m², albumin in g/dL, and platelets in 10⁹/L. AST and ALT must use the same units so their ratio is valid. This calculator applies the equation directly and rounds only the displayed result.
Two cutoffs create three interpretation zones. A score below -1.455 is considered a low likelihood of advanced fibrosis, while a score above 0.676 is considered a high likelihood. Scores between those cutoffs are indeterminate. The indeterminate zone is intentional: it avoids forcing a confident classification where the model provides insufficient separation. Current care pathways may combine NFS with FIB-4, transient elastography, enhanced liver fibrosis testing, imaging, specialist review, or biopsy depending on patient context and local guidance.
NFS performance varies by setting and patient characteristics. Age contributes directly to the equation, which can increase false-positive classifications in older adults and affect interpretation in younger people. Acute illness, changing aminotransferases, low platelets from another cause, altered albumin from inflammation or nutrition, and laboratory unit errors can also distort the score. The tool is designed for NAFLD populations and should not be casually applied to unrelated liver diseases or pediatric patients.
Use contemporaneous, verified values and confirm units before calculation. A low score does not guarantee absence of fibrosis, and a high score does not establish a diagnosis on its own. The result should be interpreted by a qualified healthcare professional alongside history, examination, alcohol exposure, medications, metabolic risk, other liver tests, and appropriate follow-up. This calculator provides educational arithmetic and must not delay urgent assessment when symptoms or laboratory findings suggest serious liver disease.
NAFLD score examples
| Clinical values | NFS | Interpretation |
|---|---|---|
| Age 35, BMI 25, AST 20, ALT 25, albumin 4.5, platelets 300, no diabetes | -4.11 | Below -1.455: low likelihood. |
| Age 50, BMI 30, AST 40, ALT 35, albumin 4.0, platelets 250, diabetes | -0.63 | Between cutoffs: indeterminate. |
| Age 65, BMI 35, AST 70, ALT 40, albumin 3.2, platelets 120, diabetes | 3.21 | Above 0.676: high likelihood. |
| Age 45, BMI 28, AST 30, ALT 40, albumin 4.2, platelets 280, no diabetes | -3.05 | Below -1.455: low likelihood. |
How to calculate the NAFLD Fibrosis Score
- Confirm that the assessment is appropriate for an adult with NAFLD.
- Enter age, BMI, AST, ALT, albumin, and platelet count using the displayed units.
- Select whether diabetes or impaired fasting glucose is present.
- Choose Calculate NAFLD Score and review the numeric score and cutoff band.
- Interpret the result with clinical context and an appropriate fibrosis pathway.
NAFLD Fibrosis Score FAQ
What does a low NAFLD Fibrosis Score mean?
A score below -1.455 suggests a low likelihood of advanced fibrosis in the population for which the model was developed. It does not completely exclude fibrosis or replace clinical follow-up.
What does an indeterminate score mean?
A result from -1.455 through 0.676 cannot confidently classify advanced fibrosis using NFS alone. Additional noninvasive testing or specialist assessment may be appropriate.
Why are AST and ALT both required?
The equation uses their ratio rather than either enzyme by itself. Both results should come from a comparable time and use the same concentration units.
Can NFS diagnose cirrhosis?
No, it estimates the likelihood of advanced fibrosis and is not a stand-alone diagnostic test. Diagnosis requires interpretation with other clinical, laboratory, and imaging evidence.
Does age affect the result?
Yes, age is a weighted term in the equation and increases the score. Clinicians should consider known age-related limitations when applying the standard cutoffs.