Generalizability of the nonalcoholic steatohepatitis Clinical Research Network histologic scoring system for nonalcoholic fatty liver disease

Abstract

Goals and background: The recently developed histologic scoring system for nonalcoholic fatty liver disease (NAFLD) by the nonalcoholic steatohepatitis (NASH) Clinical Research Network (CRN) is becoming increasingly popular. However, its generalizability to a community setting has not been evaluated. We conducted a study to compare a community general pathologist to an expert hepatopathologist in assessing NAFLD using the NASH CRN scoring system.

Study: Forty-eight consecutive patients with suspected NAFLD underwent liver biopsy. Histologic features of interest such as steatosis, lobular inflammation, balloon degeneration, fibrosis, NAFLD Activity Score (NAS), and the presence of NASH were scored in a blinded fashion by the 2 pathologists on 2 separate occasions 3 months apart.

Results: The mean (± SD) length of the liver biopsy samples was 25 ± 5 mm. Interobserver agreement (κ) between 2 pathologists was 0.62 (0.45-0.80) for steatosis, 0.44 (0.23-0.65) for lobular inflammation, 0.25 (0.11-0.38) for ballooning, 0.40 for NAS (0.28-0.52), and 0.35 (0.19-0.52) for fibrosis. The 2 pathologists diagnosed "definite NASH" in a similar proportion of patients (56% vs. 57%), but their interobserver agreement was only 0.46 (0.24-0.67) as they both diagnosed different levels of NASH (borderline vs. definite) in different subjects. Intraobserver agreement was generally comparable for steatosis, lobular inflammation, NAS, and diagnosis of NASH, but not for fibrosis.

Conclusions: Clinically important differences exist between community general pathologist and expert hepatopathologist in assessing NAFLD using the NASH CRN scoring system. More studies are needed to investigate its suitability for community-based clinical practice.

Figure 1. Relationship between NAFLD Activity Score and the Diagnosis of NASH by Pattern Recognition by the Community General Pathologist

For each activity score represented on the X axis, the percentage of observations with a particular histological diagnosis is shown on the Y axis. The total number of observations for each activity score is shown across the top of the graph.

Figure 2. Relationship between NAFLD Activity Score and the Diagnosis of NASH by Pattern Recognition by the Expert Hepatopathologist

For each activity score represented on the X axis, the percentage of observations with a particular histological diagnosis is shown on Y axis. The total number of observations for each activity score is shown across the top of the graph.