Eligible patients
In this prospective multicenter study, 165 patients were initially eligible, and 2 were excluded because of known CAD or poor image quality. A total of 163 patients from six institutions were analyzed, including: Kajikawa Hospital (n=29), Juntendo University (n=40), JA Hiroshima Hospital (n=30), Hiroshima Prefectural Hospital (n=21), Hiroshima City Asa Hospital (n=12), and Matsuyama Heart Center (n=30). The average age was 68.4 ± 12.9 years, and 99 (61%) were men. Seventy-four (46%) patients complained of atypical chest pain and 28 (17%) complained of typical chest pain, whereas the remaining 61 (37%) patients had no chest symptoms. The study sample included 28 (17%) patients with cerebral infarction and eight (5%) patients with peripheral artery disease.
Chest CT examinations were prospectively performed in 105 patients (65%), and coronary CT scans were performed simultaneously. In the remaining 58 patients, chest CT examinations performed within 79 days before coronary CT [43 (27%) cases were performed within 1 to 7 days] were used for analysis. The Agaston score ranged from 0 to 3166 (median, 90). The prevalence of obstructive CAD was 43 (27% patients) (Table 1).
Interobserver agreements of each visual CAC measurement
There was an excellent interobserver agreement of each CAC measurement between the two observers (R² = 0.913 and 0.955, Weston score, and Ca-slice#, respectively) (Supplemental Figure 1).
Agreements between visual CAC measurement and Agatston score
In the cohort, 20%, 32%, 22%, and 27%, had none (0), mild (1–99), moderate (100–400), and severe (>400) Agatston classes, respectively.
Figure 2 shows the distribution of Agatson classes by Weston score (0–12) (Panel A) and by Ca-slice# (0–17) (Panel B). Weston score was classified according to the hierarchy of the Agatston score, and graded as none, 0; mild, 1–4; moderate, 5–8; and severe, 9–12. The Weston score class was in good agreement with the Agatston score class [kappa value = 0.604 (95% CI 0.511–0.696)] (Panel C). Similarly, Ca-slice# was graded as none = 0, mild = 1–4, moderate = 5–8, and severe = 9–17. Ca-slice# also showed good agreement with the Agatston score class [kappa value = 0.794 (95% CI 0.720–0.869)] (Panel D).
Weston score classes agreed with Agatston score classes in 115 (71%) patients, but disagreed with the remaining 48 (29%) patients. The Ca-slice# classes agreed with Agatston score classes in 138 (85%) patients, but disagreed with the remaining 25 (15%) patients. In each visual score, differences in clinical and imaging factors and CT machines were compared between the agreed and disagreed groups, but no significant parameters affecting their agreements were found.
Diagnostic performance for obstructive CAD using non-ECG gated calculated and visual estimated CAC scores
After excluding 8 patients with non-diagnostic studies, the diagnostic power was evaluated in 155 patients. Obstructed CAD was found in 43 patients (27%).
ROC analyses (Figure 3) showed comparisons of diagnostic performance in detecting obstructive CAD using three scores. The C-statistics of Agatston score, Weston score, and Ca-slice# were 0.750 (95% CI 0.646–0.831), 0.721 (95% CI 0.618–0.805), and 0.706 (95% CI 0.603–0.792), respectively (p = 0.046). Ca-slice# had a significantly lower c-statistic than the Agatston score (difference 0.044 [95% CI 0.008–0.080], P = 0.016).
In comparison, when divided into four classes, the c-statistics of 4 the 4-grade hierarchies of Agatston score, Weston score, and Ca-slice# were 0.722 (95% CI 0.587–0.826), 0.706 (95% CI, 0.609–0.781), and 0.718 (95% CI 0.618–0.801), respectively, with no statistically significant differences (P = 0.798).
When each cutoff point was set at an Agatston score of 179, Weston score of 6, and Ca-slice# of 4, the sensitivity and specificity, respectively, for identifying obstructive CAD were 70% and 79% for Agatston score, 65% and 74% for Weston score, and 81% and 61% for Ca-slice#. When the cutoff point was set at a moderate class of each score, corresponding to an Agatston score of ≥100, Weston score of ≥6, and Ca-slice# of ≥4, the sensitivity and specificity, respectively, for identifying obstructive CAD were 79% and 63% for Agatston score, 84% and 51% for Weston score, and 81% and 61% for Ca-slice# (Table 3).