Inter-core lab variability in analyzing quantitative coronary angiography for bifurcation lesions: A post-hoc analysis of a randomized trial

Objectives This study sought to evaluate inter-core lab variability in quantitative coronary angiography (QCA) analysis of bifurcation lesions. Background QCA of bifurcation lesions is challenging. To date there are no data available on the inter-core lab variability of bifurcation QCA analysis. Methods The randomized Tryton IDE (Tryton Pivotal IDE Coronary Bifurcation Trial) compared the Tryton Side Branch Stent (Tryton Medical, Durham, North Carolina) with balloon angioplasty as side branch treatment. QCA was performed in an angiographic subcohort (n = 326) at 9-month follow-up. Inter-core lab variability of QCA analysis between the Cardiovascular Research Foundation and the Cardialysis core labs was evaluated before and after alignment of the used QCA methodology using angiographic data derived from this angiographic follow-up cohort. Results In the original analysis, before alignment of QCA methodology, the mean difference between the core labs (bias) was large for all QCA parameters with wide 95% limits of agreement (1.96 × SD of the bias), indicating marked variability. The bias of the key angiographic endpoint of the Tryton trial, in-segment percentage diameter stenosis (%DS) of the side branch, was 5.5% (95% limits of agreement: -26.7% to 37.8%). After reanalysis, the bias of the in-segment %DS of the side branch reduced to 1.8% (95% limits of agreement: -16.7% to 20.4%). Importantly, after alignment of the 2 core labs, there was no longer a difference between both treatment groups (%DS of the side branch: treatment group A vs. group B: 34.4 ± 19.4% vs. 32.4 ± 16.1%, p = 0.340). Conclusions Originally, a marked inter-core lab variability of bifurcation QCA analysis was found. After alignment of methodology, inter-core lab variability decreased considerably and impacted angiographic trial results. This latter finding emphasizes the importance of using the same methodology among different core labs worldwide.