Abstract: Objective This study was conducted to investigate application of magnetic resonance proton density fat fraction (MRI-PDFF) in predicting nonalcoholic steatohepatitis (NASH) in overweight and obese children with nonalcoholic fatty liver disease (NAFLD). Methods 74 overweight and 28 obese children with NAFLD were enrolled in 903^rd Hospital, Jiangyou, between December 2022 and December 2023, and all underwent liver biopsies for diagnosis of NASH. MRI-PDFF was obtained by MRI scan, liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) were determined by Fibroscan and area under receiver operating characteristic (AUC) was applied to predict diagnostic performance. Results Of the 102 overweight/obese children, histo-pathological examination diagnose simple nonalcoholic fatty liver (SNFL) in 75 cases and NASH in 27 cases; basic mass index, serum ALT, AST, TG, MRI-PDFF, LSM and CAP in children with NASH were (32.2±3.4)kg/m², (92.7±31.3)U/L, (96.8±34.1)U/L, (3.1±1.2)mmol/L, (12.5±4.7)%, (11.7±1.4)kPa and (370.4±146.9)dB/m, all significantly different compared to[(26.7±2.2)kg/m², (38.2±4.4)U/L, (33.0±3.4)U/L, (2.3±0.7)mmol/L, (7.7±2.0)%, (6.2±1.0)kPa and (262.3±61.2)dB/m, respectively, P<0.05)] in those with SNFL; percentages of overweight and obese in children with NASH were 37.0% and 63.0%, much different compared to 85.3% and 14.7% in those with SNFL (P<0.05); ROC analysis showed that the AUC was 0.87(95%CI:0.80-0.93), with sensitivity (Se) of 81.5% and specificity (Sp) of 85.3%, when MRI-PDFF was 11.9% as the cut-off-value in predicting NASH, while the AUC was 0.81(95%CI:0.78-0.89), with Se of 85.2% and Sp of 58.7% (P<0.05), when LSM was 10.8 kPa and CAP was 310.5dB/m combination as the cut-off-value. Conclusion The diagnostic performance of MRI-PDFF in predicting NASH in overweight/obese children with NAFLD is satisfactory, and from the economic and convenient point of view, we recommend Fibroscan for screening.

Key words: Nonalcoholic steatohepatitis, Magnetic resonance imaging, Proton density fat fraction, Fibroscan, Children, Diagnosis