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The NAFLD Fibrosis Score (NFS) is a validated, non-invasive clinical prediction tool that uses six routine clinical and laboratory parameters to estimate the likelihood of advanced hepatic fibrosis (stages F3–F4) in patients with Non-Alcoholic Fatty Liver Disease (NAFLD) — now increasingly referred to as Metabolic-Associated Fatty Liver Disease (MAFLD) or Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). It was developed by Angulo et al. (2007) from a cohort of 733 NAFLD patients with liver biopsy and validated in 629 additional patients across multiple countries. NAFLD is the most common liver disease worldwide, affecting approximately 25% of the global adult population, and a subset of these patients develop non-alcoholic steatohepatitis (NASH/MASH) with progressive fibrosis — the key predictor of long-term outcomes including cirrhosis, hepatocellular carcinoma, liver transplantation, and liver-related mortality. The NFS formula is: −1.675 + (0.037 × age in years) + (0.094 × BMI in kg/m²) + (1.13 × IFG/diabetes, coded as 1 if present, 0 if absent) + (0.99 × AST/ALT ratio) − (0.013 × platelet count in ×10^9/L) − (0.66 × albumin in g/dL). Two validated cut-off points define three risk categories: NFS below −1.455 predicts absence of advanced fibrosis (F0–F2) with high negative predictive value (~88%); NFS above +0.676 predicts presence of advanced fibrosis (F3–F4) with reasonable positive predictive value (~82%); NFS between −1.455 and +0.676 is the indeterminate zone where further assessment with liver biopsy or transient elastography (FibroScan) is recommended.
NAFLD Fibrosis Score = -1.675 + (0.037 × age) + (0.094 × BMI) + (1.13 × IFG/DM) + (0.99 × AST/ALT ratio) - (0.013 × platelets ×10^9/L) - (0.66 × albumin g/dL)
- 1Collect required inputs: patient age (years), BMI (kg/m²), presence of impaired fasting glucose (IFG, ≥5.6 mmol/L) or type 2 diabetes (coded as 1 = yes, 0 = no), AST/ALT ratio, platelet count (×10^9/L), and serum albumin (g/dL).
- 2Calculate AST/ALT ratio: divide AST (U/L) by ALT (U/L). In normal liver, ALT > AST giving ratio <1; in advanced fibrosis/cirrhosis, AST > ALT gives ratio >1.
- 3Apply the NFS formula: −1.675 + (0.037 × age) + (0.094 × BMI) + (1.13 × IFG_DM) + (0.99 × AST/ALT) − (0.013 × platelets) − (0.66 × albumin).
- 4Interpret the result: NFS < −1.455 = low fibrosis risk (F0–F2 likely); NFS −1.455 to +0.676 = indeterminate (further assessment needed); NFS > +0.676 = high fibrosis risk (F3–F4 likely).
- 5For indeterminate zone: perform transient elastography (FibroScan; advanced fibrosis threshold 8–10 kPa) or enhanced liver fibrosis (ELF) panel.
- 6Refer patients with NFS >+0.676 or FibroScan >8–10 kPa to hepatology for management of advanced fibrosis and hepatocellular carcinoma surveillance.
- 7Repeat NFS annually in patients with NAFLD/MAFLD on lifestyle intervention or pharmacological therapy to track fibrosis progression or regression.
Low NFS has high NPV (~88%) for ruling out advanced fibrosis; no biopsy or FibroScan needed
A negative NFS well below -1.455 reliably identifies a patient unlikely to have advanced fibrosis. Lifestyle intervention (weight loss 5–10%) is the primary management.
AST/ALT ratio >1 in NAFLD is an ominous sign of advanced fibrosis or cirrhosis
An AST/ALT ratio above 1 in NAFLD with diabetes and high BMI produces a score above the high-risk cut-off. Urgent hepatology referral is warranted.
Low platelets suggest portal hypertension; thrombocytopaenia in NAFLD indicates likely cirrhosis
An NFS of 2.598 strongly predicts advanced fibrosis. Thrombocytopenia (128 × 10^9/L) and low albumin in this context suggest cirrhosis may already be present.
Fibrosis regression (improvement by ≥1 stage) is achievable with ≥10% body weight loss in NAFLD
Serial NFS monitoring demonstrates clinically meaningful fibrosis regression following significant sustained weight loss and diabetes remission.
Primary care and diabetology: screening patients with type 2 diabetes and elevated liver enzymes for advanced NAFLD fibrosis using NFS or FIB-4., representing an important application area for the Steatohepatitis Risk in professional and analytical contexts where accurate steatohepatitis risk calculations directly support informed decision-making, strategic planning, and performance optimization
Hepatology clinic: risk stratification of newly referred NAFLD patients to prioritise FibroScan or liver biopsy in those with high NFS., representing an important application area for the Steatohepatitis Risk in professional and analytical contexts where accurate steatohepatitis risk calculations directly support informed decision-making, strategic planning, and performance optimization
Pre-bariatric surgery assessment: NFS helps identify which obese patients have advanced fibrosis requiring hepatology input before weight-loss surgery., representing an important application area for the Steatohepatitis Risk in professional and analytical contexts where accurate steatohepatitis risk calculations directly support informed decision-making, strategic planning, and performance optimization
Treatment response monitoring: serial NFS calculation tracking fibrosis improvement after sustained weight loss, diabetes remission, or novel pharmacological therapy., representing an important application area for the Steatohepatitis Risk in professional and analytical contexts where accurate steatohepatitis risk calculations directly support informed decision-making, strategic planning, and performance optimization
Clinical trials: NFS as a stratification variable and secondary endpoint in MASH/NASH drug trials., representing an important application area for the Steatohepatitis Risk in professional and analytical contexts where accurate steatohepatitis risk calculations directly support informed decision-making, strategic planning, and performance optimization
NAFLD in Type 2 Diabetes
{'title': 'NAFLD in Type 2 Diabetes', 'body': 'Type 2 diabetes is the strongest independent risk factor for NAFLD progression to NASH and advanced fibrosis. The co-occurrence of NAFLD and T2DM dramatically worsens prognosis for both conditions: NAFLD worsens insulin resistance and glycaemic control, while T2DM accelerates hepatic steatosis and fibrogenesis. EASL-EASD-EASO 2023 guidelines recommend annual FIB-4 calculation in all patients with T2DM. GLP-1 receptor agonists (semaglutide, liraglutide) and SGLT2 inhibitors (empagliflozin, dapagliflozin) improve both glycaemic control and NAFLD histology.'}
NAFLD in Children and Adolescents
{'title': 'NAFLD in Children and Adolescents', 'body': 'NAFLD affects 3–10% of children and adolescents globally, rising to 40–70% in obese children. It presents differently from adult NAFLD: lobular inflammation is the predominant histological feature (rather than the periportal pattern common in adults). FIB-4 performs poorly in paediatric populations. Alanine aminotransferase (ALT) above age- and sex-specific thresholds on two occasions 3 months apart is the recommended trigger for hepatology referral in overweight/obese children. Lifestyle modification (diet and exercise) is the only evidence-based treatment.'}
NAFLD and Cardiovascular Risk
{'title': 'NAFLD and Cardiovascular Risk', 'body': 'NAFLD is an independent risk factor for cardiovascular disease — the leading cause of death in NAFLD patients, ahead of liver-related mortality except in those with cirrhosis. The mechanisms include: hepatic overproduction of atherogenic lipoproteins (VLDL, small dense LDL), systemic inflammation, insulin resistance, and endothelial dysfunction. Cardiovascular risk assessment (Framingham, QRISK3) should be performed in all NAFLD patients, and statin therapy (which is safe in NAFLD) should not be withheld due to fear of hepatotoxicity in patients with metabolic liver disease.'}
NAFLD in the Indeterminate Zone
{'title': 'NAFLD in the Indeterminate Zone', 'body': 'A significant proportion of NAFLD patients (30–40%) fall in the NFS indeterminate zone between -1.455 and +0.676, where the score cannot reliably predict fibrosis stage. In these patients, FibroScan (transient elastography) is the recommended next step: liver stiffness <8 kPa = unlikely to have advanced fibrosis; 8–12 kPa = indeterminate or significant fibrosis; >12 kPa = likely advanced fibrosis/cirrhosis. Magnetic resonance elastography (MRE) has superior accuracy but is expensive and less available.'}
| NFS Score | Fibrosis Risk | Likely Histology | Recommended Action |
|---|---|---|---|
| < -1.455 | Low | F0–F2 (mild to moderate fibrosis) | Annual monitoring; lifestyle intervention; re-screen in 2–3 years |
| -1.455 to +0.676 | Indeterminate | Cannot distinguish F0-F2 from F3-F4 | FibroScan; ELF panel; consider liver biopsy if clinical uncertainty |
| > +0.676 | High | F3–F4 (advanced fibrosis or cirrhosis) | Hepatology referral; FibroScan; HCC surveillance if cirrhosis; pharmacological treatment consideration |
What is the difference between NAFLD, NASH, MAFLD, and MASLD?
NAFLD (Non-Alcoholic Fatty Liver Disease) is an umbrella term for fat accumulation in the liver not explained by alcohol use or secondary causes. NASH (Non-Alcoholic Steatohepatitis) is the progressive subtype characterised by hepatic steatosis plus inflammation and ballooning injury, often with fibrosis. In 2020, an international expert panel proposed renaming NAFLD to MAFLD (Metabolic-Associated Fatty Liver Disease) to better reflect its metabolic origins. In 2023, Delphi consensus renamed it again to MASLD (Metabolic Dysfunction-Associated Steatotic Liver Disease) with MASH for its inflammatory subtype. These name changes have not yet been universally adopted; NAFLD and NASH remain in widespread clinical and research use.
Why does AST/ALT ratio increase in advanced liver fibrosis?
In early NAFLD and NASH, ALT is typically higher than AST, reflecting active hepatocellular inflammation predominantly involving ALT-rich liver cells. As fibrosis advances and liver cell mass decreases, ALT production falls disproportionately relative to AST. Additionally, ALT is produced exclusively in hepatocytes, while AST is also produced in muscle, heart, and red blood cells. In advanced cirrhosis, the falling ALT (fewer functioning hepatocytes) and rising AST (often combined with mitochondrial injury) causes the ratio to exceed 1.0. An AST/ALT ratio >2 strongly suggests alcoholic hepatitis or advanced cirrhosis.
What other non-invasive fibrosis tests are available?
Non-invasive fibrosis assessment tools include: FibroScan (transient elastography) — the most validated, measures liver stiffness in kPa; >8 kPa = significant fibrosis, >12 kPa = likely cirrhosis. ELF (Enhanced Liver Fibrosis) panel — measures hyaluronic acid, PIIINP, and TIMP-1; FIB-4 Index — age × AST / (platelets × √ALT), cut-offs <1.3 (low risk) and >2.67 (high risk); APRI score — AST / (platelet count); MRI elastography — gold standard for non-invasive assessment but expensive and limited availability.
What is the FIB-4 Index and how does it compare to NFS?
FIB-4 = Age(years) × AST(U/L) / (Platelet count(×10^9/L) × √ALT(U/L)). Cut-offs: <1.3 = low risk (F0–F1); 1.3–2.67 = indeterminate; >2.67 = high risk (F3–F4). FIB-4 is simpler than NFS (4 variables vs 6) and has similar discriminatory performance. Current NICE and EASL guidelines recommend FIB-4 as the initial screening tool for liver fibrosis in primary care and diabetes clinics due to its simplicity. NFS provides slightly more information in the intermediate range. Both tools should be followed by FibroScan in the indeterminate zone.
Who should be screened for NAFLD fibrosis?
EASL, NICE, and AASLD guidelines recommend screening for NAFLD/MAFLD fibrosis in patients with: type 2 diabetes, metabolic syndrome (obesity + dyslipidaemia + hypertension ± insulin resistance), incidentally detected elevated liver enzymes, unexplained thrombocytopaenia, incidental hepatic steatosis on imaging, and obesity (BMI >30). In diabetic patients, a FIB-4 <1.3 reliably excludes advanced fibrosis; those with FIB-4 ≥1.3 should proceed to FibroScan. Universal NAFLD screening in diabetes clinics with FIB-4 is cost-effective and recommended by the 2023 EASL-EASD-EASO Clinical Practice Guidelines.
What treatments are available for NASH/MASH with fibrosis?
Lifestyle modification (10% body weight loss significantly reduces fibrosis, and >15% can lead to complete NASH resolution in a proportion of patients) remains the cornerstone treatment. FDA-approved pharmacological therapies: resmetirom (Rezdiffra, a thyroid hormone receptor-β agonist) was approved by the FDA in March 2024 for MASH with liver fibrosis (F2–F3) — the first drug specifically approved for NASH/MASH. GLP-1 receptor agonists (semaglutide) have shown significant fibrosis improvement in trials. FXR agonists (obeticholic acid) and PPAR agonists (lanifibranor) are in late-stage trials. Bariatric surgery achieves the most profound and sustained liver histological improvement.
What is the risk of hepatocellular carcinoma in NAFLD?
Patients with NAFLD-related cirrhosis have an annual HCC incidence of 2–4%, comparable to other causes of cirrhosis. Notably, a significant proportion of NAFLD-related HCC (up to 20–30%) develops in non-cirrhotic livers with advanced fibrosis (F3) — a pattern less common in viral hepatitis. Risk factors for NAFLD-HCC include: cirrhosis (strongest), male sex, age >60, diabetes, obesity, alcohol use (even moderate), and genetic factors (PNPLA3 I148M variant). Six-monthly liver ultrasound + AFP surveillance is recommended for all NAFLD cirrhosis patients.
Can NAFLD fibrosis score be used to monitor treatment response?
Yes — the NFS can be serially calculated to track fibrosis progression or regression over time. A decrease in NFS associated with weight loss, diabetes remission, or pharmacological treatment reflects improved fibrosis status. However, NFS has significant variability and the indeterminate zone limits its precision for detecting small changes. FibroScan (liver stiffness measurement) is more sensitive for detecting short-term changes and is the preferred tool for treatment response monitoring in clinical trials.
专业提示
Remember the pattern that indicates advanced fibrosis in NAFLD without calculating the full score: older age + higher BMI + diabetes or IFG + AST/ALT ratio approaching or exceeding 1 + falling platelets + lower albumin. When more than two or three of these are present simultaneously, the NFS is almost certainly above +0.676 — prompt hepatology referral without waiting for the formal calculation is clinically appropriate.
你知道吗？
The NAFLD Fibrosis Score was developed using liver biopsies from patients enrolled across international centres in the USA, Spain, Australia, and Italy — at a time when the global prevalence of NAFLD was first being recognised. Its lead author, Pablo Angulo, estimated when publishing the score in 2007 that NAFLD affected 20–30% of the US adult population. That estimate has now been revised upward to 25–30% globally, and with the MASLD renaming in 2023, some metabolic criteria-based estimates now place the global prevalence as high as 32–38%.
参考资料
- ›Angulo P et al — NAFLD Fibrosis Score (Hepatology 2007)
- ›EASL-EASD-EASO Clinical Practice Guidelines for MASLD (J Hepatol 2023)
- ›NICE NG49 — Non-Alcoholic Fatty Liver Disease (2016 updated 2023)
- ›Harrison SA et al — Resmetirom for MASH Fibrosis (NEJM 2024)
- ›Sanyal AJ — AASLD Practice Guidance on NAFLD (Hepatology 2023)