How many times should we repeat measurements of the ultrasound-guided attenuation parameter for evaluating hepatic steatosis?

PURPOSE: This retrospective study aimed to determine the number of times the ultrasound-guided attenuation parameter (UGAP) should be measured during the evaluation of hepatic steatosis. METHODS: Patients with suspected nonalcoholic fatty liver disease who underwent two UGAP repetition protocols (six-repetition [UGAP_6] and 12-repetition [UGAP_12]) and measurement of the controlled attenuation parameter (CAP) using transient elastography between October 2020 and June 2021 were enrolled. The mean attenuation coefficient (AC), interquartile range (IQR)/median, and coefficient of variance (CV) of the two repetition protocols were compared using the paired t test. Moreover, the diagnostic performances of UGAP_6 and UGAP_12 were compared using the area under the receiver operating characteristic (AUROC) curve, considering the CAP value as a reference standard. RESULTS: The study included 160 patients (100 men; mean age, 50.9 years). There were no significant differences between UGAP_6 and UGAP_12 (0.731±0.116 dB/cm/MHz vs. 0.734±0.113 dB/cm/MHz, P=0.156) and mean CV (7.6±0.3% vs. 8.0±0.3%, P=0.062). However, the mean IQR/median of UGAP_6 was significantly lower than that of UGAP_12 (8.9%±6.0% vs. 9.8%±5.2%, P=0.012). In diagnosing the hepatic steatosis stage, UGAP_6 and UGAP_12 yielded comparable AUROCs (≥S1, 0.908 vs. 0.897, P=0.466; ≥S2, 0.883 vs. 0.897, P=0.126; S3, 0.832 vs. 0.834, P=0.799). CONCLUSION: UGAP had high diagnostic performance in diagnosing hepatic steatosis, regardless of the number of repetitions (six repetitions vs. 12 repetitions), with maintained reliability. Therefore, six UGAP measurements seem sufficient for evaluating hepatic steatosis using UGAP.