The development and validation of magnetic resonance elastography for fibrosis staging in primary sclerosing cholangitis.

OBJECTIVES: To develop and internally validate MR elastography (MRE) quantified liver stiffness (LS) cut-off values for distinguishing early/moderate fibrosis from cirrhosis in primary sclerosing cholangitis (PSC) against non-invasive fibrosis test of vibration-controlled transient elastography (VCTE).

METHODS: Sixty-seven patients were enrolled prospectively at a tertiary care centre to undergo MRE and VCTE. MRE-quantified LS was calculated using three region-of-interest (ROI) methods: Trace, Average and Maximum. Each ROI method was compared with the reference standard of VCTE. Internal validation was performed with bootstrapping. Univariable and multivariable linear regression determined independent predictors for MRE-quantified LS and final Mayo Risk Score (MRS).

RESULTS: MRE-quantified LS by Trace ROI method had the highest sensitivity [87.5%; 95% confidence interval (CI), 66.0-96.8] and specificity (96.1%; 95%CI, 89.6-99.0) for distinguishing cirrhosis; and was the strongest predictor of final MRS (β, 0.44; 95% CI, 0.27-0.61). Alkaline phosphatase twice the normal upper limit (β, 1.55; 95% CI, 0.95-2.17), abnormal bilirubin (β, 1.27; 95% CI, 0.41-2.14) and thrombocytopaenia (β, 0.79; 95% CI, 0.12-1.46) were independent predictors of LS.

CONCLUSIONS: MRE has a higher correlation with MRS than VCTE; and though MRE is possibly influenced by severe cholestasis and portal hypertension, MRE-quantified LS is an independent predictor of worse MRS.

KEY POINTS: • MRE is valid and reliable in assessing cirrhosis in PSC, and MRE-quantified Liver stiffness (LS) score was the strongest predictor of final Mayo Risk Score (MRS). • Trace ROI performs best for distinguishing moderate fibrosis from cirrhosis and has the highest correlation with Mayo Risk Score (MRS). • Cholestasis, hyperbilirubinaemia and portal hypertension may influence MRE LS score.