Development and validation of a new histological score for pediatric non-alcoholic fatty liver disease

Background & Aims: Pediatric non-alcoholic fatty liver disease (NAFLD) may present with a distinct histopathological pattern characterized by the presence of predominant portal-based injury and portal inflammation (PI). We aimed at developing a new grading score for pediatric NAFLD to be used in clinical trials that takes into account the presence of PI and the weight of histological features. Methods: Our training set consisted of 203 children with biopsy-proven NAFLD. The diagnosis of non-alcoholic steatohepatitis (NASH) was based on Brunt's criteria. Histological features were scored: steatosis (0-3), lobular inflammation (0-3), ballooning (0-2), and PI (0-2). Logistic regression analysis was performed to apply weight to each feature. The new score was called the Pediatric NAFLD Histological Score or PNHS. The validation set consisted of 100 children with NAFLD. Results: The mean age of the initial cohort was 12.4 ± 3.4 years and significant fibrosis (fibrosis stage ≥2) was present in 26 patients (12.8%). NASH was diagnosed in 135 patients with a mean NAS of 4.5 ± 1.4. The mean PNHS in the NASH group was 89 ± 20.5 compared to 21.9 ± 24.5 in the "not NASH" group, p <0.001. PNHS correlated with the presence of NASH according to the pathologist's diagnosis, better than the NAFLD activity score (NAS), p = 0.011. The area under the ROC curve (AUC) for the diagnosis of NASH was 0.96 for PNHS. Similar findings were observed in the validation set with an AUC of 0.94. Conclusions: PNHS may be used for histological grading of pediatric NAFLD with excellent correlation with the presence of NASH.