Comparison of interobserver agreement of magnetic resonance elastography with histopathological staging of liver fibrosis

MR elastography (MRE) can serve as an accurate surrogate marker of liver fibrosis. For any diagnostic test that is to replace the current reference standard, interobserver agreement should be at least as good and preferably better. The objective of this study was to perform a head-to-head comparison of the interobserver agreements of MRE and liver fibrosis staging on biopsy in a single cohort of hepatitis patients. One hundred and three patients with viral hepatitis B or C who had a liver biopsy underwent MRE. Two readers independently selected a region-of-interest (ROI) in the liver to derive elasticity values. Two pathologists first independently staged fibrosis on biopsies using the METAVIR classification and subsequently held a consensus meeting. Interobserver agreements of elasticity values and fibrosis stages were assessed with intraclass correlation coefficients (ICC). MRE and biopsy data were available for 85/103 patients. ICC of pathologists staging fibrosis was almost perfect at 0.91 (95% CI 0.86-0.94). ICC for MRE readers was significantly (P < 0.0001) higher at 0.99 (95% CI 0.98-1.00). Interobserver agreement for liver fibrosis staging was almost perfect for both histopathology and MRE, with a significant higher agreement for MRE. Its high interobserver agreement and reliable accuracy support the use of MRE as a non-invasive screening tool for liver fibrosis.