Ethnic Differences in the Diagnostic Accuracy of a Quantitative Ultrasound-Derived Fat Fraction Estimator for Hepatic Steatosis: External Validation in Asian and Caucasian Cohorts.

Ultrasound fat fraction estimation (USFF) using quantitative ultrasonography (QUS) is a promising method for assessing liver fat in metabolic dysfunction-associated steatotic liver disease (MASLD). However, its performance across different ethnicities remains unclear. This study aimed to externally validate and compare USFF accuracy in Asian and Caucasian cohorts. This retrospective analysis used QUS data from three institutions. Participants underwent QUS and magnetic resonance imaging of the proton density fat fraction (MRI-PDFF), the reference standard. A multivariable regression model was developed using two QUS parameters. Linear regression was used to estimate fat fraction, with adjusted R2 values assessing model fit. The diagnostic performance of USFF for hepatic fat content thresholds (≥ 5%, ≥ 10%, ≥ 20%) was evaluated using the area under the receiver operating characteristic curve (AUC). The development set included 427 South Korean participants, while the validation set comprised 100 from Hungary and 79 from Italy. R2 values were 0.689, 0.702, and 0.485 for the development, internal validation, and external validation sets, respectively. AUC for detecting hepatic steatosis (MRI-PDFF ≥ 5%) was 0.939 (development) and 0.863 (external validation). Using a cutoff > 0.513, USFF achieved 85.1% sensitivity and 87.4% specificity. USFF is effective but shows variability across populations, highlighting the need for ethnicity-specific models.