GI ToolsGastroenterology and hepatology

NAFLD Activity Score (NAS)

The NAFLD Activity Score (Kleiner) grades activity on a liver biopsy. It was designed to measure change in trials, not to diagnose steatohepatitis, which is a pattern judgement by the pathologist. Fibrosis is staged separately.

Steatosis
Lobular inflammation (foci per 200× field)
Hepatocyte ballooning
Fibrosis stage (not part of the NAS)

Enter the values above.

Related resources: MASLD

Reference

Kleiner DE, Brunt EM, Van Natta M, et al. Design and validation of a histological scoring system for nonalcoholic fatty liver disease. Hepatology. 2005;41(6):1313-1321.