Purpose:To evaluate the diagnostic accuracy of ultrasonography (US) for the assessment of hepatic steatosis in severely obese adolescents, with proton magnetic resonance (MR) spectroscopy as the reference standard, and to provide insight on the infl uence of prevalence on predictive values by calculating positive and negative posttest probabilities.
Materials and Methods:This prospective study was institutional review board approved. All participants, and/or their legal representatives, gave written informed consent. Sensitivity, specifi city, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the overall presence of steatosis and for the presence of substantial (moderate to severe) steatosis. Positive and negative posttest probabilities were calculated and plotted against prevalence.
Results:A total of 104 children (47 male, 57 female) were prospectively included.
Conclusion:Positive US results in severely obese adolescents cannot be used to accurately predict the presence and severity of hepatic steatosis, and additional imaging is required. Negative US results exclude the presence of substantial steatosis with acceptable accuracy. Steatosis prevalence differs among specifi c populations, strongly infl uencing posttest probabilities.q RSNA, 2011 1