Assessment of Fibrosis in Liver Transplant Recipients: Diagnostic Performance of Shear Wave Elastography (SWE) and Correlation of SWE Findings With Biopsy Results

OBJECTIVE Liver transplant patients are monitored for rejection and hepatic fibrosis and often undergo liver biopsies. The purpose of the present study is to determine whether noninvasive shear wave elastography (SWE) can quantify fibrosis in liver transplant recipients, with the aim of decreasing and possibly eliminating unnecessary biopsies for patients with suspected or progressive hepatic fibrosis. MATERIALS AND METHODS Between May 1, 2015, and December 31, 2017, our prospective study evaluated 111 adult liver transplant patients (age range, 23-79 years) who underwent 147 ultrasound (US) SWE examinations of the right hepatic lobe followed by biopsies. SWE values were compared with the histologic fibrosis (Metavir) scores of the biopsy samples. SWE threshold values were determined using classification and regression tree analysis by anchoring to the degree of fibrosis. The sensitivity, specificity, positive predictive value, and negative predictive value (with 95% Cls) were calculated on the basis of the threshold value. Overall prediction accuracy was estimated using the AUC value from the ROC curve. RESULTS From the 147 US SWF, examinations and liver biopsies, consistent threshold values were identified for patients with no or minimal fibrosis (Metavir scores of F0 and F1, respectively) compared with significant fibrosis (Metavir scores of F2, F3, or F4). A median SWE value of 1.76 m/s or less denoted no or minimal fibrosis, whereas a value greater than 1.76 m/s denoted significant fibrosis. The sensitivity of US SWE examinations in classifying fibrosis was 0.77 (95% CI, 0.5-0.93). The specificity, positive predictive value, and negative predictive value were 0.79 (95% CI, 0.71-0.86), 0.33 (95% CI, 0.19-0.49), and 0.96 (95% CI, 0.91-0.99), respectively. CONCLUSION Liver transplant patients may avoid liver biopsy if US SWE examination shows a median shear wave velocity of 1.76 or less, which corresponds to a Metavir score of F0 or F1, denoting no or minimal fibrosis.