Comparison of QCA systems

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Abstract
Aims: Excellent agreement between different ‘second generation’ systems for quantitative coronary arteriography (QCA) has been found in in vitro measurements. To verify the quality and stability of QCA when used in clinical practice, three QCA systems (AWOS, Cardio, and CMS) were used in a representative set of coronary artery lesions. Methods and results: This set consisted of angiographic stenosis images of 57 patients which varied in stenosis severity and morphology. The process of image acquisition, calibration, and measurement was strictly standardized to eliminate procedural sources of error. Three observers performed QCA five times in each lesion with each QCA system. Interobserver variability was low (Dnorm 0.01–0.05 mm, Dmin 0.01–0.02 mm, %stenosis 0.3–0.7%). Values of system precision were excellent (Dnorm 0.11–0.13 mm, Dmin 0.04–0.06 mm, %stenosis 2.1–2.6%). Comparison of measurements between the three QCA systems revealed good agreement (range of mean differences for Dnorm 0.03–0.12 mm, Dmin 0.04–0.11 mm, and%stenosis 0.5–3.6%) and high correlation (corr 0.902–0.977). There was a tendency to measure smaller values for Dmin and consequently to identify more severe stenoses with the AWOS system than with the Cardio and CMS systems. All QCA results were compared to measurements done with the Brown Dodge method to reveal systematic failure of the QCA measurements. These results showed excellent agreement without any systematic deviation (mean differences for Dnorm 0.01–0.08 mm, Dmin 0.02–0.06 mm, and%stenosis 1.3–1.8%). None of the differences were statistically significant. Conclusion: We therefore conclude that using the defined version of the AWOS, Cardio, and CMS systems, there is no difference in precision or accuracy when used for QCA of coronary artery lesions.