Non-Invasive Assessment of Hepatic Steatosis in Patients with NAFLD Using Controlled Attenuation Parameter and 1H-MR Spectroscopy

Introduction: Non-invasive assessment of steatosis and fibrosis is of growing relevance in non-alcoholic fatty liver disease (NAFLD). H-1-Magnetic resonance spectroscopy (H-1-MRS) and the ultrasound-based controlled attenuation parameter (CAP) correlate with biopsy proven steatosis, but have not been correlated with each other so far. We therefore performed a headto- head comparison between both methods. Methods: Fifty patients with biopsy-proven NAFLD and 15 healthy volunteers were evaluated with H-1-MRS and transient elastography (TE) including CAP. Steatosis was defined according to the percentage of affected hepatocytes: S1 5-33%, S2 34-66%, S3 >= 67%. Results: Steatosis grade in patients with NAFLD was S1 36%, S2 40% and S3 24%. CAP and H-1-MRS significantly correlated with histopathology and showed comparable accuracy for the detection of hepatic steatosis: areas under the receiveroperating characteristics curves were 0.93 vs. 0.88 for steatosis >= S1 and 0.94 vs. 0.88 for >= S2, respectively. Boot-strapping analysis revealed a CAP cut-off of 300 dB/m for detection of S2-3 steatosis, while retaining the lower cut-off of 215 dB/m for the definition of healthy individuals. Direct comparison between CAP and H-1-MRS revealed only modest correlation (total cohort: r = 0.63 [0.44, 0.76]; NAFLD cases: r = 0.56 [0.32, 0.74]). For detection of F2-4 fibrosis TE had sensitivity and specificity of 100% and 98.1% at a cut-off value of 8.85 kPa. Conclusion: Our data suggest a comparable diagnostic value of CAP and H-1-MRS for hepatic steatosis quantification. Combined with the simultaneous TE fibrosis assessment, CAP represents an efficient method for non-invasive characterization of NAFLD. Limited correlation between CAP and H-1-MRS may be explained by different technical aspects, anthropometry, and presence of advanced liver fibrosis.