Conventional magnetic resonance imaging (MRI) techniques that measure hepatic steatosis are limited by T1 bias, T₂* decay and multi‐frequency signal‐interference effects of protons in fat. Newer MR techniques such as the proton density‐fat fraction (PDFF) that correct for these factors have not been specifically compared to liver biopsy in adult patients with non‐alcoholic fatty liver disease (NAFLD).

To examine the association between MRI‐determined PDFF and histology‐determined steatosis grade, and their association with fibrosis.

A total of 51 adult patients with biopsy‐confirmed NAFLD underwent metabolic‐biochemical profiling, MRI‐determined PDFF measurement of hepatic steatosis and liver biopsy assessment according to NASH‐CRN histological scoring system.

The average MRI‐determined PDFF increased significantly with increasing histology‐determined steatosis grade: 8.9% at grade‐1, 16.3% at grade‐2, and 25.0% at grade‐3 with P ≤ 0.0001 (correlation: r² = 0.56, P < 0.0001). Patients with stage‐4 fibrosis, when compared with patients with stage 0–3 fibrosis, had significantly lower hepatic steatosis by both MRI‐determined PDFF (7.6% vs. 17.8%, P < 0.005) and histology‐determined steatosis grade (1.4 vs. 2.2, P < 0.05). NAFLD patients with grade 1 steatosis were more likely to have characteristics of advanced liver disease including higher average AST:ALT (0.87 vs. 0.60, P < 0.02), GGT (140 vs. 67, P < 0.01), and INR (1.06 vs. 0.99, P < 0.01), higher stage of fibrosis and hepatocellular ballooning.

MRI‐determined proton density‐fat fraction correlates with histology‐determined steatosis grade in adults with NAFLD. Steatosis is non‐linearly related to fibrosis progression. In patients with NAFLD, a low amount of hepatic steatosis on imaging does not necessarily indicate mild disease.