ToolsCalculators
NAFLD activity score (NAS)
Histologic grading of non-alcoholic fatty liver disease activity.
NAFLD activity score (NAS)
Steatosis (% of hepatocytes)
Lobular inflammation (foci per 200x field)
Hepatocellular ballooning
Result0 points
Largely not diagnostic of NASH (>=5 correlates with NASH, <=2 usually not NASH).
- Category
- Largely not diagnostic of NASH
When to use
- Standardised semiquantitative reporting of NAFLD disease activity on liver biopsy, chiefly for trials.
Formula
NAS = steatosis (0-3) + lobular inflammation (0-3) + ballooning (0-2). Range 0-8.
Pearls and pitfalls
- NAS was designed for measuring change in trials, not as a stand-alone diagnosis of NASH.
- Fibrosis is staged separately and is not part of the NAS.