Prospective comparison of transient elastography, MRI and serum scores for grading steatosis and detecting non-alcoholic steatohepatitis in bariatric surgery candidates

•NAFLD/NASH is common in morbidly obese patients undergoing bariatric surgery.•Non-invasive diagnosis of NAFLD/NASH is an unmet need in this population.•We compared MRI-PDFF, CAP and serum scores for grading steatosis and diagnosing NASH, using liver biopsy as a reference.•Applicability of magnetic resonance imaging was better than that of Fibroscan.•MRI-PDFF outperformed CAP for diagnosing and grading steatosis, as well as excluding NASH.