Proposal for a histological scoring and grading system for non-alcoholic fatty liver disease

: Aim/Background: The spectrum of histopathological features in non‐alcoholic fatty liver disease (NAFLD) has been well described. At least two scoring systems have been established. We propose here a system in which numerical scores are obtained using the different features. Methods: Twenty‐five cases of well‐defined NAFLD were idengified. Two pathologists blinded to idengifiers and clinical data independently scored the liver biopsies twice for portal fibrosis (PF: 0–6), lobular inflammation and necrosis (LIN: 0–3), Mallory bodies (MB: 0–3), hepatocyte ballooning (HB: 0–3), perisinusoidal fibrosis (PSF: 0–3) and fatty change (FC: 1–4). The κ statistic tested observer concordance. Non‐parametric measures of correlation and hierarchical cluster analysis were used to elaborate a grading system. Results: A broad spectrum of NAFLD was observed. Intra‐ and interobserver concordance was satisfactory. An activity score was created (AS: 0–12) as the sum of LIN, MB, HB and PSF, but not FC. A system for severity of NAFLD was developed: Grade 1 (PF: 0–2 and AS: 0–4), Grade 2 (PF: 3 or AS: 5–7) and Grade 3 (PF: 4–6 or AS: 8–12). Diabetes, elevated alkaline phosphatase and decreased platelets were associated with advanced grade. Conclusions: This simple, reproducible NAFLD score produces a three‐tier severity grade. This numerical system may prove useful in assessing disease severity and interval changes.