Diagnostic Performance of Ultrasound-Guided Attenuation Parameter (UGAP) for Hepatic Steatosis Assessment: Comparison with MRI-PDFF and Evaluation of Cohort-Derived Thresholds

Background/Objectives: To evaluate the diagnostic performance of ultrasound-guided attenuation parameter (UGAP) for the assessment of hepatic steatosis in a population at risk for metabolic dysfunction-associated steatotic liver disease (MASLD), using MRI proton density fat fraction (PDFF) as the reference standard, and to also derive optimal population-specific diagnostic thresholds. Methods: In this single-center prospective study, 64 adults at risk for MASLD underwent UGAP measurement and MRI-PDFF. UGAP was performed according to standardized manufacturer-recommended protocols and standardized on the right hepatic lobe. Hepatic steatosis was staged using established MRI-PDFF thresholds. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis. Cohort-UGAP cut-offs were derived using the Youden index. Associations between UGAP and clinical parameters were assessed using correlation and regression analyses. Results: UGAP correlated strongly with MRI-PDFF (ρ = 0.82, p < 0.001). The areas under the ROC curve (AUCs) for detecting mild, moderate, and severe steatosis were 0.86, 0.96, and 0.96, respectively. Right-lobe acquisitions outperformed left-lobe measurements, while four-region averaging yielded the highest diagnostic performance. UGAP values were associated with BMI, waist circumference, and liver enzymes. Conclusions: UGAP provides an accurate noninvasive assessment of hepatic steatosis, demonstrating high overall diagnostic agreement with MRI-PDFF. Right-lobe acquisition and multi-regional averaging further improve its performance. While cohort-specific threshold optimization may enhance clinical applicability, larger studies are needed to fully confirm its accuracy in advanced stages.