Five published prediction rules were validated (Tables 2 and 3): Diamond & Forrester [22], Pryor et al. [23], Morise et al. 1994 [24], Morise et al. 1997 [17] and Shaw et al. [25]. The Diamond & Forrester prediction rule includes age, sex and type of chest pain, all of which were significant predictors of obstructive CAD in our dataset and with an area under the ROC curve (AUC) of 0.798. Including CTCS increased the AUC to 0.890, which was a statistically significant improvement (p < 0.001). In the expanded model age and sex were no longer significant predictors (Table 2).
Table 2 Comparison of multivariate logistic regression models
Variables Model 1: Diamond & Forrester 1979 Model 2: Pryor et al. 1993 Model 3: Morise et al. 1994
No calcium score Calcium score No calcium score Calcium score No calcium score Calcium score
OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI
ln CTCSa (CT calcium score)  1.97 1.60, 2.41  1.93 1.55, 2.41  1.87 1.52, 2.29
Age  1.05 1.02, 1.08 0.98 0.95, 1.02 1.02 0.95, 1.09 0.93 0.86, 1.01  1.05 1.01, 1.08 0.98 0.95, 1.02
Male sex  2.97 1.57, 5.61 1.64 0.79, 3.42 0.19 0.00, 12.20 0.02 0.00, 1.91  3.48 1.77, 6.83 2.05 0.94, 4.45
Typical chest pain  6.61 3.67, 11.89  5.34 2.70, 10.56  5.44 2.90, 10.18  5.22 2.52, 10.81  5.44 2.94, 10.05  4.91 2.43, 9.91
Smoking 0.08 0.00, 9.40 0.06 0.00, 11.40
Dyslipidaemia 10.90 0.19, 610.99 2.43 0.03, 195.86  3.03 1.63, 5.61 1.94 0.96, 3.94
Diabetes  2.81 1.07, 7.38 2.14 0.71, 6.42  2.61 1.02, 6.73 2.22 0.74, 6.65
Age–smoking 1.04 0.97, 1.13 1.03 0.95, 1.12
Age–dyslipidaemia 0.98 0.92, 1.05 1.00 0.93, 1.07
Sex–smoking 1.77 0.36, 8.84 3.82 0.66, 22.09
Age–sex 1.05 0.98, 1.12 1.07 1.00, 1.15
Oestrogen
Hypertension
Family history
Dyslipidaemia–family history
Obesity
BMI
 
AUCb 0.798 0.742, 0.854 0.890 0.851, 0.930 0.838 0.789, 0.887 0.901 0.863, 0.938 0.831 0.780, 0.881 0.899 0.861, 0.937
LR testc  p < 0.001  p < 0.001  p < 0.001
Odds ratios (ORs) in bold typeface are statistically significant
aNatural logarithm of CTCS + 1
bArea under the receiver operating characteristic curve
cLikelihood ratio test comparing model without CTCS and model including CTCS
Table 3 Comparison of multivariate logistic regression models
Variables Model 4: Morise et al. 1997 Model 5: Shaw et al. 1998
No calcium score Calcium score No calcium score Calcium score
OR 95% CI OR 95% CI OR 95% CI OR 95% CI
ln CTCSa (CT calcium score)  1.87 1.50, 2.31  1.86 1.51, 2.30
Intercept
Age  1.05 1.01, 1.09 0.99 0.95, 1.03  1.05 1.02, 1.08 0.98 0.95, 1.02
Male sex  3.15 1.29, 7.70 1.37 0.48, 3.95  3.42 1.74, 6.74 2.05 0.94, 4.45
Typical pain  5.56 2.94, 10.51  4.82 2.36, 9.86  5.50 2.96, 10.21  4.91 2.44, 9.90
Smoking 1.53 0.72, 3.24 1.03 0.44, 2.39 1.63 0.80, 3.30 1.04 0.47, 2.27
Dyslipidaemia  3.20 1.29, 7.95 1.80 0.62, 5.22  3.04 1.63, 5.66 1.95 0.96, 3.94
Diabetes 2.66 0.98, 7.26 2.01 0.61, 6.61  2.85 1.10, 7.39 2.24 0.74, 6.75
Age–smoking
Age–dyslipidaemia
Sex–smoking
Age–sex
Oestrogen 0.78 0.33, 1.86 0.53 0.19, 1.48
Hypertension 1.83 0.93, 3.60 1.31 0.62, 2.79
Family History 2.02 0.77, 5.29 1.14 0.38, 3.39
Dyslipidaemia–family history 0.74 0.21, 2.60 1.15 0.28, 4.82
Obesity 0.88 0.31, 2.48 0.65 0.20, 2.12
BMI 0.99 0.88, 1.13 1.05 0.91, 1.22
 
AUCb 0.840 0.792, 0.889 0.898 0.859, 0.936 0.833 0.783, 0.883 0.899 0.861, 0.937
LR testc  p < 0.001  p < 0.001
Odds ratios (ORs) in bold typeface are statistically significant
aNatural logarithm of CTCS + 1
bArea under the receiver operating characteristic curve
cLikelihood ratio test comparing model without CTCS and model including CTCS