Magnetic resonance imaging proton density fat fraction and selected quantitative ultrasound methods for hepatic steatosis: histology-referenced diagnostic performance and longitudinal responsiveness—a systematic review and meta-analysis

PURPOSE: To synthesize histology-referenced diagnostic performance at study-selected thresholds and the longitudinal responsiveness of magnetic resonance imaging proton density fat fraction (MRI-PDFF) and selected quantitative ultrasound methods in adults with non-alcoholic fatty liver disease/metabolic dysfunction-associated steatotic liver disease. METHODS: Four databases were searched from database inception through July 1, 2026. Sensitivity, specificity, and odds ratios were pooled with 95% confidence intervals using heterogeneity-selected fixed- or random-effects models. Small-study effects were assessed using funnel plots and Begg tests; longitudinal changes were pooled when change-score standard deviations were reported. RESULTS: In total, 44 articles were included: 34 contributed histology-referenced diagnostic data, and 11 were assessed for longitudinal responsiveness, with 1 article contributing to both. At steatosis grade (S) ≥ 1/S ≥ 2/S ≥3, MRI-PDFF sensitivity and specificity was 93.6%/81.5%/83.1% and 87.1%/86.7%/83.2%, respectively; the controlled attenuation parameter (CAP) was 86.8%/81.2%/86.4% and 98.9%/71.0%/64.6%, respectively. The attenuation coefficient/attenuation imaging sensitivity/specificity was 83.2%/98.1%, 86.4%/79.9%, and 99.3%/76.4%, respectively. Ultrasound-guided attenuation parameter and ultrasound-derived fat fraction evidence was limited. Three head-to-head longitudinal studies included 298 participants, of whom only 158 had analyzable change-score data; in these, pooled changes were -4.53 percentage points for MRI-PDFF and -12.71 dB/m for the CAP. Thirty-two of the 34 diagnostic studies were at high-risk of bias from cohort-selected thresholds. Begg tests did not detect significant small-study effects, although their power was very limited in analyses that included only 2 or 3 studies. CONCLUSION: At study-selected thresholds, MRI-PDFF showed balanced sensitivity and specificity across steatosis grades, whereas quantitative ultrasound varied by method, platform, and threshold. These findings support comparative synthesis but do not establish validated cut-offs or superiority of either modality. CLINICAL SIGNIFICANCE: Study-selected thresholds limit clinical translation. MRI-PDFF proton density fat fraction and quantitative ultrasound are complementary, with use depending on clinical purpose, platform, and precision needs.