BACKGROUND: Amidst the global rise of metabolic dysfunction-associated steatotic liver disease (MASLD), driven by increasing obesity rates, there is a pressing need for precise, non-invasive diagnostic tools. Our research aims to validate MRI Proton Density Fat Fraction (MRI-PDFF) utility, compared to liver biopsy, in grading hepatic steatosis in MASLD. METHODS: A systematic search was conducted across Embase, PubMed/Medline, Scopus, and Web of Science until January 13, 2024, selecting studies that compare MRI-PDFF with liver biopsy for hepatic steatosis grading, defined as grades 0 (<
5% steatosis), 1 (5-33% steatosis), 2 (34-66% steatosis), and 3 (>
66% steatosis). RESULTS: Twenty-two studies with 2844 patients were included. The analysis showed high accuracy of MRI-PDFF with AUCs of 0.97 (95% CI = 0.96-0.98) for grade 0 vs ≥ 1, 0.91 (95% CI = 0.88-0.93) for ≤ 1 vs ≥ 2, and 0.91 (95% CI = 0.88-0.93) for ≤ 2 vs 3, diagnostic odds ratio (DOR) from 98.74 (95% CI = 58.61-166.33) to 23.36 (95% CI = 13.76-39.68), sensitivity and specificity from 0.93 (95% CI = 0.88-0.96) to 0.76 (95% CI = 0.63-0.85) and 0.93 (95% CI = 0.88-0.96) to 0.89 (95% CI = 0.84-0.93), respectively. Likelihood ratio (LR) + ranged from 13.3 (95% CI = 7.4-24.0) to 7.2 (95% CI = 4.9-10.5), and LR - from 0.08 (95% CI = 0.05-0.13) to 0.27 (95% CI = 0.17-0.42). The proposed MRI-PDFF threshold of 5.7% for liver fat content emerges as a potential cut-off for the discrimination between grade 0 vs ≥ 1 (p = 0.075). CONCLUSION: MRI-PDFF is a precise non-invasive technique for diagnosing and grading hepatic steatosis, warranting further studies to establish its diagnostic thresholds. CLINICAL RELEVANCE STATEMENT: This study underscores the high diagnostic accuracy of MRI-PDFF for distinguishing between various grades of hepatic steatosis for early detection and management of MASLD, though further research is necessary for broader application. KEY POINTS: MRI-PDFF offers precision in diagnosing and monitoring hepatic steatosis. The diagnostic accuracy of MRI-PDFF decreases as the grade of hepatic steatosis advances. A 5.7% MRI-PDFF threshold differentiates steatotic from non-steatotic livers.