Interobserver variations of plaque severity score and segment stenosis score in coronary arteries using 64 slice multidetector computed tomography: a substudy of the ACCURACY trial

Background: Assessing the severity of coronary plaque for the risk stratification and management of coronary artery disease is important. Multidetector computed tomography has been shown to be a useful tool to measure coronary plaque; however, interreader variability is a concern.

Objective: We measured interobserver variations of plaque severity score (PSS) and segment stenosis score (SSS) as measured by the total plaque severity score (TPS) and total segment stenosis score (TSS).

Methods: Cardiac CT scans (n = 221) of the ACCURACY trial were interpreted by 3 different readers blinded to patient characteristics. PSS (mild, 1; moderate, 2; and severe, 3) and SSS (stenosis 1%-29%, 1; 30%-49%, 2; 50%-69%, 3; and ≥70%, 4) were calculated with the 15-segment American Heart Association model. TPS and TSS were determined by summing the segments for each interpreter. TPS and TSS were compared for correlation and variation among any 2 of the 3 readers.

Results: A highly significant correlation was observed among any 2 of the 3 readers for both TPS and TSS. For TPS, the r = 0.91, 0.93, 0.94 (P < 0.001) for A vs B, B vs C, A vs C, respectively, and for TSS, r = 0.91, 0.92, 0.93 (P < 0.001) for A vs B, B vs C, A vs C, respectively. On Bland Altman plot, the mean difference between the scores of any 2 readers was 3.33 ± 3.93, 1.65 ± 2.88, and 1.68 ± 2.92 for TPS and 4.19 ± 4.73, 2.54 ± 4.02, and 1.65 ± 3.18 for TSS.

Conclusion: Semiquantitative measures of coronary plaque burden, including the TPS and TSS, can be determined with a high degree of interobserver agreement, suggesting their potential role as tools to aid in the assessment of coronary heart disease.