BACKGROUND: There is significant disparity in the reported incidence of moderate and severe paravalvular aortic regurgitation (PAR) between the Placement of Aortic Transcatheter Valves (PARTNER) I and PARTNER II trials, which may be related to the echocardiographic methodologies used by separate core laboratories. To further explore the variability in echocardiographic interpretation of PAR, agreement between the grading of PAR by the core laboratory of PARTNER IIB was compared with that by a consortium of echocardiography core laboratory directors. METHODS: The PARTNER IIB core laboratory reevaluated patients using primarily the circumferential extent of the regurgitant jet for PAR. A consortium of echocardiography core laboratory directors was formed to evaluate the echocardiographic images and to grade PAR and central and total aortic regurgitation in a randomly chosen subset of the randomized patients in the PARTNER IIB trial using a multiwindow, multiparametric approach. Both a four-class scale (none or trace, mild, moderate, and severe) and a seven-class (none, trace, mild, mild to moderate, moderate, moderate to severe, and severe) scale were used. Levels of grading agreement between the consortium and original core laboratory in both scales were determined using weighted ¿ statistics. RESULTS: Only 87 patients assessed for PAR by the consortium could be paired with readings by the PARTNER IIB core laboratory. Using the four-class grading scheme the weighted ¿ statistic for PAR was 0.481 (95% confidence limits, 0.367, 0.595). Using the seven-class scale, the weighted ¿ statistic for PAR was 0.517 (95% confidence limits, 0.431, 0.607). For either grading scheme, 15.9% of patients graded by the PARTNER IIB core laboratory as having moderate PAR would have been graded as having mild PAR using the multiparametric approach. Similar results were seen for central and total aortic regurgitation assessments. CONCLUSIONS: Using primarily the circumferential extent criteria, the PARTNER IIB core laboratory overestimated the severity of PAR compared to the consortium using a multi-parametric approach. Although a more granular classification scheme for PAR may slightly improve concordance between core laboratories, differences in the incidence of moderate or severe PAR are likely related to differences in grading methodology. A multiparametric approach is advocated, and other echocardiographic methods for assessing PAR deserve further study.