Ultrasound-guided Attenuation Parameter (UGAP) for the quantification of liver steatosis using the Controlled Attenuation Parameter (CAP) as the reference method

Abstract

Aim: Nonalcoholic Fatty Liver Disease (NAFLD) is increasing in frequency in daily practice and evaluation of liver steatosis, fibrosis and inflammation severity are essential for prognosis assessment. The aim was to evaluate the usefulness of a new liver steatosis quantification system - Ultrasound-Guided Attenuation Parameter (UGAP) from General Electric Healthcare, using Controlled Attenuation Parameter (CAP) as the reference method. Material and method: 179 consecutive subjects, in whom liver steatosis was assessed in the same session using UGAP, implemented on LOGIQ E10 system (GE Healthcare), and CAP (FibroScan, EchoSens). To discriminate between steatosis stages by CAP, we used the cut-offs recommended by the manufacturer: S1 (mild) – 230 dB/m, S2 (moderate) – 275 dB/m, S3 (severe) – 300 dB/m. Results: We classified our cohort by means of CAP into the following groups: S0 (no steatosis): 48/176 (27.2%), S1 (mild): 56/176 (31.6%), S2 (moderate): 14/176 (7.3%) and S3 (severe): 59/176 (33.9%). The mean UGAP values increased with the steatosis grade and for each group were the following: S0: 198.3±25.7 dB/m, S1: 216.86±26.3 dB/m, S2: 237.79±26.3 dB/m, and S3: 270.8±31.62 dB/m respectively (p<0.001). A very good positive correlation was found between UGAP and CAP values (r=0.73, p<0.0001). The best cut-off values for predicting different grades of liver steatosis using CAP as the reference were: S1 - 192.5 dB/m (AUC 0.83); S2 – 231 dB/m (AUC 0.90) and S3 – 248 dB/m (AUC 0.91). Conclusion: UGAP seems to be a good method for liver steatosis quantification and correlates strongly with CAP values.