Prospective comparison of transient elastography, magnetic resonance imaging and serum scores for grading steatosis and detecting nonalcoholic steatohepatitis in bariatric surgery candidates

Abstract Background & Aims Non-invasive diagnosis of nonalcoholic steatohepatitis (NASH) is an unmet need in morbidly obese patients with suspected nonalcoholic fatty liver disease (NAFLD). We compared prospectively the performance of transient elastography (TE), magnetic resonance imaging (MRI), and three serum scores for diagnosing NAFLD, grading steatosis and detecting NASH in bariatric surgery candidates. Methods Of 186 patients screened, 152 underwent liver biopsy (LB), used as reference for NAFLD (S>5%), steatosis grading (S>33%, S>66%) and NASH diagnosis. LBs were read by a single expert pathologist. MRI-based proton density fat fraction (MRI-PDFF) was measured in an open-bore, vertical field 1.0T scanner and controlled attenuation parameter (CAP) by TE, using the XL probe. Serum scores (ST: SteatoTestTM; HSI: hepatic steatosis index and FLI: fatty liver index) were also calculated. Results Applicability of MRI was better than that of FibroScan (98% vs. 79%; p 5%, S>33% and S>66% and NASH, respectively. TE had an AUROC of 0.80 for significant fibrosis (F0-F1 vs. F2-F3). MRI-PDFF had AUROCs of 0.97, 0.95, 0.92 and 0.84 for S>5%, S>33% and S>66% and NASH, respectively. When compared head-to-head in the 97 patients with all valid tests available, MRI-PDFF outperformed CAP for grading steatosis (S>33%, AUROC 0.97 vs. 0.78; p 66%, AUROC 0.93 vs. 0.75; p=0.0015) and diagnosing NASH (AUROC 0.82 vs. 0.68; p=0.0056). When compared in "intention to diagnose" analysis, MRI-PDFF outperformed CAP, HSI and FLI for grading steatosis (S>5%, S>33% and S>66%). Conclusion MRI-PDFF outperforms CAP for diagnosing NAFLD, grading steatosis and excluding NASH in morbidly obese patients undergoing bariatric surgery. Lay summary Non-invasive tests for detecting fatty liver and steatohepatitis, the active form of the disease, have not been well studied in obese patients who are candidate to bariatric surgery. The most popular tests for this purpose are FibroScan, allowing to measure the controlled attenuation parameter (CAP), and magnetic resonance imaging, allowing to measure the proton density fat fraction (MRI-PDFF). We found that, when taking liver biopsy as reference, MRI-PDFF performed better than CAP for detecting and grading fatty liver as well as excluding steatohepatitis in morbidly obese patients undergoing bariatric surgery.