BMI Metrics Are Poor Predictors of Pediatric Nonalcoholic Fatty Liver Disease Severity

Alternative BMI metrics are superior to BMI z score (BMIz) in tracking obesity but have not been evaluated in patients with nonalcoholic fatty liver disease (NAFLD). Our objective was to evaluate whether BMI-adjusted z score (BMIaz) or BMI expressed as a percentage of the 95th percentile (%BMIp95) are better predictors of degree of alanine aminotransferase (ALT) elevation, a surrogate for NAFLD severity, compared with BMIz in patients with NAFLD. A retrospective study of 776 subjects aged 2-18 years with BMIz > 1.0 followed in a NAFLD subspecialty clinic was conducted. Regression analysis was used to determine predictors of elevated ALT. There was no association between BMIz, BMIaz, or %BMIp95 and degree of ALT elevation using linear or logistic regression. These results do not support the use of alternative BMI metrics for evaluating NAFLD severity. Future studies should investigate longitudinal assessments and correlation with histology.