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.

Complex ultrasound evaluation of non-alcoholic fatty liver disease. “One stop shop” with new ultrasound-based techniques.

“…The authors classified the cohort by means of CAP into the following groups: S0 (no steatosis), S1 (mild), S2 (moderate) and S3 (severe). The mean UGAP values increased with the steatosis grade and a very good positive correlation was found between UGAP and CAP values (r=0.73, p<0.0001) [6]. This method seems to provide an objective estimation of liver steatosis severity but is also a very good method to assess the efficacy of treatments during follow-up As many ultrasound systems have incorporated modules for steatosis and also fibrosis quantification, we have reached the time when such "multiparametric" ultrasound systems may enter clinical practice providing important and valuable information regarding the severity of steatosis and fibrosis in the NAFLD population.…”

“…Ultrasound (US) was the first-line imaging test used in clinical practice in individuals with suspected NAFLD [1]. Although it has a good accuracy for moderate-to-severe steatosis (sensitivity of 85% and specificity of 94%) its value in detect-ing steatosis of less than 20% is low [1,5,6]. Moreover, it cannot diagnose fibrosis and steatohepatitis, very important pathologic stages toward a severe liver disease.…”

“…Moreover, it cannot diagnose fibrosis and steatohepatitis, very important pathologic stages toward a severe liver disease. Another limitation of US is the impossibility to monitor disease progression and to assess various therapeutical methods [1,2,5,6]. Recent studies obtained better results using quantitative ultrasound (sonographic hepatorenal index, hepatic attenuation rate, Steatoscore, acoustic structure quantification [3][4][5]).…”

“…Elastography based techniques -Transient Elastography (TE) FibroScan, point Shear Wave Elastography (pSWE) and Two-Dimensional Shear Wave Elastography (2D-SWE) [5][6][7][8][9] -are used for the assessment of liver fibrosis in many liver diseases including NAFLD [1][2][3][4][5]. Using a XL probe FibroScan yields an AUROC of 0.82 for significant fibrosis, 0.86 for advanced fibrosis, and 0.94 for cirrhosis in a group of patients with NAFLD [1].…”

“…In this issue of Medical Ultrasonography Bende at al assessed the accuracy of ultrasound-guided attenuation parameter (UGAP) for the quantification of liver steatosis in patients with NAFLD using CAP as the reference method [6]. UGAP measures the attenuation coefficient based on a reference phantom that includes glass bead particles of attenuating materials with known attenuation coefficient [6]. The authors classified the cohort by means of CAP into the following groups: S0 (no steatosis), S1 (mild), S2 (moderate) and S3 (severe).…”