Diagnostic Performance of Ultrasound in Detecting Hepatic Steatosis in Non-Alcoholic Fatty Liver Disease Considering MRI Proton Density Fat Fraction as the Reference Standard

Abstract

Introduction: The increasing incidence of Non-Alcoholic Fatty Liver Disease (NAFLD) will burden the health care system. There is a pressing need to devise an accurate non-invasive method to detect and quantify hepatic steatosis (HS) in NAFLD.Goal: To evaluate the diagnostic efficacy of conventional ultrasound (US) to predict the presence and degree of HS in NAFLD considering MRI Proton Density Fat Fraction (PDFF) as the reference standard.Methods: The study comprised sixty subjects with high clinical suspicion of NAFLD. The US was performed to assess four defined signs (abnormal echogenicity of liver, loss of echogenicity of portal vein, poor diaphragm visualization and posterior beam attenuation). MRI IDEAL IQ software-generated fat-fraction maps were used to measure PDFF values as the average of 24 regions of interest (ROIs) in eight liver segments. The sensitivity, specificity, NPV, PPV and diagnostic accuracy of US signs and their combinations were calculated with the MRI PDFF values (≥6.5 % vs <6.5 %) as the reference standard.Results: The presence of posterior beam attenuation and obscuration of the diaphragm in the US showed excellent sensitivity and NPV (100%) for detecting grade 3 HS. The presence of altered liver echotexture and loss of echogenicity of the portal vein showed excellent sensitivity and NPV (100%) for detecting grade 2 HS.Conclusion: The sensitivity and negative predictive value of various US signs and their combinations for detecting hepatic steatosis were excellent. Thus, the conventional ultrasound must be considered a satisfactory screening tool for the exclusion of NAFLD.