NAFLD Fibrosis Score Calculator

Calculate the NAFLD Fibrosis Score (NFS) to assess the probability of advanced liver fibrosis in patients with non-alcoholic fatty liver disease. Recommended by NICE and EASL guidelines for non-invasive fibrosis assessment.

Important Clinical Disclaimer: The NAFLD Fibrosis Score Calculator is intended for use by qualified healthcare professionals only. It is for educational and informational purposes and should not replace clinical judgement. Always interpret results alongside the full clinical picture and follow your local guidelines and protocols.
NAFLD Fibrosis Score Parameters
Patient Demographics
Weight (kg) / Height (m)²
IFG = Impaired Fasting Glucose (fasting glucose 6.1-6.9 mmol/L)
Laboratory Values
Aspartate aminotransferase
Alanine aminotransferase
Normal: 150-400 ×10⁹/L
Normal: 35-50 g/L
About NAFLD Fibrosis Score

The NAFLD Fibrosis Score (NFS) was developed to predict advanced liver fibrosis (F3-F4) in patients with non-alcoholic fatty liver disease without requiring liver biopsy.

Key features:

  • Non-invasive assessment of fibrosis
  • Uses readily available clinical and laboratory data
  • High negative predictive value for excluding advanced fibrosis
  • Endorsed by NICE, EASL, and AASLD guidelines
NFS is most useful for ruling out advanced fibrosis in low-risk patients. Indeterminate scores require further testing.
Score Interpretation
NFS Score Interpretation Fibrosis Stage
<-1.455 Low probability of advanced fibrosis Likely F0-F2
-1.455 to 0.676 Indeterminate Further testing needed
>0.676 High probability of advanced fibrosis Likely F3-F4
F0 = No fibrosis, F4 = Cirrhosis
Diagnostic Performance

For excluding advanced fibrosis (NFS <-1.455):

  • Sensitivity: 77%
  • Specificity: 71%
  • Negative Predictive Value (NPV): 93%

For detecting advanced fibrosis (NFS >0.676):

  • Sensitivity: 43%
  • Specificity: 96%
  • Positive Predictive Value (PPV): 90%
NICE NAFLD Pathway
  1. Identify NAFLD (ultrasound, raised LFTs, metabolic syndrome)
  2. Calculate fibrosis score (NFS, FIB-4, or ELF test)
  3. Low risk (NFS <-1.455): Manage in primary care, lifestyle intervention, repeat assessment in 3 years
  4. Indeterminate: FibroScan or ELF test for further stratification
  5. High risk (NFS >0.676): Refer to hepatology for specialist assessment

NAFLD Assessment Pathway (NICE NG49)

Low Risk (NFS <-1.455)

Management in Primary Care:

  • Lifestyle modification (weight loss, exercise)
  • Manage metabolic risk factors (diabetes, hypertension, dyslipidaemia)
  • Avoid alcohol excess
  • Repeat fibrosis assessment every 3 years
  • Annual cardiovascular risk assessment
Indeterminate (-1.455 to 0.676)

Further Assessment Required:

  • Request FibroScan (transient elastography)
  • Or ELF (Enhanced Liver Fibrosis) blood test
  • Consider FIB-4 if not already done
  • If FibroScan <8 kPa: manage as low risk
  • If FibroScan ≥8 kPa: refer to hepatology
High Risk (NFS >0.676)

Specialist Referral:

  • Refer to hepatology/gastroenterology
  • FibroScan to confirm fibrosis stage
  • Consider liver biopsy if diagnostic uncertainty
  • HCC surveillance if cirrhosis confirmed
  • Assess for varices if F4/cirrhosis
  • Discuss emerging pharmacological treatments

Comparing Non-Invasive Fibrosis Tests

Test Components Advantages Limitations
NFS Age, BMI, diabetes, AST/ALT, platelets, albumin
  • Free, uses routine blood tests
  • Well validated
  • Good NPV for advanced fibrosis
  • ~30% indeterminate results
  • Less accurate in elderly, diabetics
FIB-4 Age, AST, ALT, platelets
  • Simpler calculation
  • Similar accuracy to NFS
  • Fewer variables needed
  • ~30% indeterminate results
  • Age-dependent cut-offs needed for >65
ELF Test Hyaluronic acid, TIMP-1, PIIINP
  • Direct fibrosis markers
  • Good accuracy
  • Fewer indeterminate results
  • Requires special blood test
  • More expensive
  • Not universally available
FibroScan Transient elastography (liver stiffness)
  • Direct measurement of liver stiffness
  • Very good accuracy
  • Results in seconds
  • Requires special equipment
  • Unreliable if BMI >30 or ascites
  • Operator dependent

Frequently Asked Questions

NAFLD (Non-Alcoholic Fatty Liver Disease) is an umbrella term that includes:

  • Simple steatosis (NAFL): Fat accumulation in the liver without significant inflammation - generally benign
  • NASH (Non-Alcoholic Steatohepatitis): Fat accumulation WITH inflammation and hepatocyte injury - can progress to fibrosis and cirrhosis

The NFS helps identify patients with advanced fibrosis regardless of whether they have simple steatosis or NASH. Patients with advanced fibrosis are at risk of developing cirrhosis and its complications.

Note: The terminology is evolving. NAFLD is increasingly being renamed to MASLD (Metabolic dysfunction-Associated Steatotic Liver Disease) to better reflect the metabolic basis of the condition.

Both NFS and FIB-4 are validated for assessing fibrosis in NAFLD and have similar diagnostic accuracy. Key considerations:

  • FIB-4: Simpler (4 variables), can be calculated with just age and routine LFTs with FBC
  • NFS: Includes BMI and diabetes status which may provide additional prognostic information

In practice:

  • Either score is acceptable as a first-line test
  • Some guidelines recommend using both and referring if either is elevated
  • If results are discordant, use FibroScan or ELF for further assessment

NICE accepts either NFS, FIB-4, or ELF test for initial fibrosis assessment in NAFLD.

NICE recommends the following monitoring intervals:

  • Low risk (NFS <-1.455): Repeat fibrosis assessment every 3 years
  • After significant weight loss: Consider repeating sooner as fibrosis may improve
  • If new metabolic risk factors develop: Repeat assessment
  • Under hepatology care: Follow specialist guidance

More frequent monitoring may be appropriate if there are changes in clinical status or laboratory values suggestive of disease progression.

The NFS was developed and validated in populations including diabetic patients, and diabetes is a component of the score. However:

  • Some studies suggest reduced accuracy in diabetic populations
  • Diabetics have higher baseline risk of NAFLD and advanced fibrosis
  • The indeterminate range may be larger in diabetics

Recommendations for diabetic patients:

  • Lower threshold for further investigation (FibroScan)
  • Consider combining with FIB-4
  • More frequent surveillance given higher progression risk

Type 2 diabetes is an independent risk factor for NASH and fibrosis progression, so a proactive approach to fibrosis assessment is warranted.

No. The NAFLD Fibrosis Score was specifically developed and validated for patients with non-alcoholic fatty liver disease.

For alcohol-related liver disease, consider:

  • FIB-4 (has some validation in alcohol-related liver disease)
  • FibroScan (validated across multiple liver disease aetiologies)
  • ELF test
  • APRI score

NAFLD definition requires:

  • Evidence of hepatic steatosis (imaging or histology)
  • No significant alcohol consumption (<20g/day women, <30g/day men)
  • Exclusion of other causes of liver disease

If a patient has both significant alcohol intake and metabolic risk factors, the liver disease may have mixed aetiology and NFS should not be used in isolation.

Disclaimer

This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

  • Always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.
  • Never disregard professional medical advice or delay seeking it because of information from this tool.
  • Clinical decision-making should always incorporate the full clinical context, patient preferences, and local protocols.
  • The creators of this tool accept no liability for decisions made based on its output.

If you are a patient: please discuss any results with your healthcare provider. This tool is designed for use by medical professionals and may not be appropriate for self-assessment.

References

  1. Angulo P, et al. The NAFLD fibrosis score: a noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology. 2007;45(4):846-854. doi:10.1002/hep.21496
  2. NICE. Non-alcoholic fatty liver disease (NAFLD): assessment and management (NG49). 2016. https://www.nice.org.uk/guidance/ng49
  3. European Association for the Study of the Liver (EASL). EASL Clinical Practice Guidelines on non-invasive tests for evaluation of liver disease severity and prognosis. J Hepatol. 2021;75(3):659-689. doi:10.1016/j.jhep.2021.05.025
  4. Chalasani N, et al. The diagnosis and management of nonalcoholic fatty liver disease: Practice guidance from the American Association for the Study of Liver Diseases. Hepatology. 2018;67(1):328-357.
  5. McPherson S, et al. Simple non-invasive fibrosis scoring systems can reliably exclude advanced fibrosis in patients with non-alcoholic fatty liver disease. Gut. 2010;59(9):1265-1269.
  6. Rinella ME, et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Hepatology. 2023;78(6):1966-1986.