REPRODUCIBILITY OF QUANTITATIVE CORONARY ANALYSIS

Because of limited storage capacity for digital images, angiographic l aboratories without cinefilm are dependent on locally performed quanti tative coronary angiography (QCA) in clinical studies. In the present study the intra- and interobserver variability, as well as variability between different laboratories and variability due to frame selection was analyzed. A total of 20 coronary lesions were studied in two diff erent digital laboratories 12 +/- 8 days apart. Images were analyzed o n-line and after being transferred to a Cardiac Work Station (CWS). Th ere was no significant difference between the measurement situations. For minimal luminal diameter (MLD) precision (SD of signed errors) ran ged from 0.12 mm to 0.20 mm, for reference diameter (RD) from 0.15 mm to 0.28 mm, and for percent diameter stenosis (DS) from 4.2% to 5.8%. Overall relative precision was obtained by normalizing the QCA paramet ers, and was 11.9% for MLD, 7.0% for RD and 8.5% for DS (p < 0.001, RD and DS compared to MLD). The overall variability in the interobserver and in the interlaboratory comparisons was 11.2% and 10.4%, respectiv ely (n.s.) (n.s.). Thus the variability of QCA performed in cinefilmle ss, digital laboratories is small, and within a range making it an use ful tool for clinical practice and group comparisons in clinical studi es. However, the error range of QCA measurements must be taken into co nsideration when judging results from individual patients.