Staging and Grading Disease Activity in Steatohepatitis

Nonalcoholic Steatohepatitis

Histological Scoring System for Nonalcoholic Fatty Liver Disease

Components of NAFLD Activity Score (NAS) and Fibrosis Staging

Nonalcoholic Steatohepatitis Clinical Research Network

NAS Components (see scoring interpretation)

Item
Score
Extent
Definition and Comment

Steatosis

0
<5% Refers to amount of surface area involved by steatosis as evaluated on low to medium power examination; minimal steatosis (<5%) receives a score of 0 to avoid giving excess weight to biopsies with very little fatty change
1
5-33%  
2
>33-66%  
3
>66%  
Lobular Inflammation
0
No foci Acidophil bodies are not included in this assessment, nor is portal inflammation
1
<2 foci/200x  
2
2-4 foci/200x  
3
>4 foci/200x  
Hepatocyte Ballooning
0
None  
1
Few balloon cells The term "few" means rare but definite ballooned hepatocytes as well as cases that are diagnostically borderline
2
Many cells/prominent ballooning Most cases with prominent ballooning also had Mallory's hyalin, but Mallory's hyaline is not scored separately for the NAS
Fibrosis Stage (Evaluated separately from NAS)
Fibrosis
0
None  
1
Perisinusoidal or periportal  
1A
Mild, zone 3, perisinusoidal "delicate" fibrosis
1B
Moderate, zone 3, perisinusoidal "dense" fibrosis
1C
Portal/periportal This category is included to accommodate cases with portal and/or peri portal fibrosis without accompanying pericellular/perisinusoidal fibrosis
2
Perisinusoidal and portal/periportal  
3
Bridging fibrosis  
4
Cirrhosis  
Total NAS score represents the sum of scores for steatosis, lobular inflammation, and ballooning, and ranges from 0-8. Diagnosis of NASH (or, alternatively, fatty liver not diagnostic of NASH) should be made first, then NAS is used to grade activity. In the reference study, NAS scores of 0-2 occurred in cases largely considered not diagnostic of NASH, scores of 3-4 were evenly divided among those considered not diagnostic, borderline, or positive for NASH. Scores of 5-8 occurred in cases that were largely considered diagnostic of NASH


Reference: Kleiner D.E., Brunt E.M., Van Natta M., Behlinh C., Contos M.J., Cummings O.W., Ferrell L.D., Liu Y.-C., Torbenson M.S., Unalp-Arida A., Yeh M., McCullough A.J., Sanyal A.J. for the Nonalcoholic Steatohepatitis Clinical Research Network. Design and validation of a histological scoring system for nonalcoholic fatty liver disease. Hepatology 41:1313-1321, 2005.


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