Reliability Criteria for Liver Stiffness Measurements with Real-Time 2D Shear Wave Elastography in Different Clinical Scenarios of Chronic Liver Disease.

Purpose Liver stiffness measurement by real-time 2-dimensional shear wave elastography (2D-SWE) lacks universal reliability criteria. We sought to assess whether previously published 2D-SWE reliability criteria for portal hypertension were applicable for the evaluation of liver fibrosis and cirrhosis, and to look for criteria that minimize the risk of misclassification in this setting. Materials and Methods In a biopsy-controlled diagnostic study, we obtained five 2D-SWE measurements of optimal image quality. Correctly classified cases of fibrosis and cirrhosis were compared to misclassified cases. We compared reliability predictors (standard deviation (SD), SD/mean, size of region of interest (ROI) and difference between a single measurement and the patient's median) with those obtained in a prior study on clinically significant portal hypertension. Results We obtained 678 2D-SWE measurements from 142 patients. Overall, the variability in liver stiffness within single 2D-SWE measurements was low (SD = 1.1 +/- 1.5kPa; SD/ mean=12 +/- 9%). Intra-observer analysis showed almost perfect concordance (intraclass correlation coefficient = 0.95; 95 % CI 0.94-0.96; average difference from median = 0.4 +/- 0.9kPa). For the diagnosis of cirrhosis, a smaller SD (optimally = 1.75 kPa) and larger ROI size (optimally = 18 mm) were associated with higher accuracy. Similarly, within the published cohort of patients assessed for portal hypertension, a low variability of measurements was associated with high reliability. Conclusion A high quality 2D-SWE elastogram ensures low variability and high reliability, regardless of indication. We recommend aiming for a combination of low standard deviation and large ROI.