Purpose: To determine the cost-effectiveness of CT calcium scoring (CTCS) and CT coronary angiography (CTCA) as a triage test prior to conventional coronary angiography (CCA) in patients with new onset stable chest pain and to study the effect of reduced radiation exposure of CTCA on the optimal strategy.
Method: Using a Markov-model, we analyzed the cost-effectiveness of: 1) No testing, 2) CTCS, if positive (defined as “any calcium”) followed by CTCA, if positive followed by CCA, 3) CTCA, if positive followed by CCA, and 4) direct CCA. For CTCS we used a sensitivity and specificity of 99.5% and 29.6% with an associated effective dose of 2.5 mSv (3.5) for men (women). For CTCA, we used a sensitivity and specificity of 97.5% and 80.8%, respectively, with an effective dose of 15 mSv (21) in men (women). The decision was analyzed from the health-care perspective using recommendations for cost-effectiveness analyses from the United Kingdom. Optimization criteria (i.e. outcomes considered) were: quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios (ICER). Extensive sensitivity analysis was performed.
Result: The cost-effectiveness of the strategies depends on the prior probability of CAD (Figure 1). Lowering the radiation exposure associated with CTCA slightly increased the indication for CTCA in men. In women, CTCA was cost-effective within a small range of prior probabilities, which increased to 18 – 45% if the dose of a CTCA was reduced to 5 mSv. The threshold probability below which CTCS is optimal was sensitive to changes in the sensitivity of CTCS. For example in men (reference case), a 98.0% sensitivity lowered the threshold from 28% to 10%, which in turn increased the indication for CTCA. 
Figure 1. The optimal diagnostic strategy (highest net health benefit, willingness-to-pay threshold = €80.000/QALY) depending on the prior probability of CAD
Conclusion: Given the high sensitivity of CTCS, the results suggest that CTCS is a cost-effective triage test to rule out CAD in both men and women with a low prior probability of CAD and that CTCA is a cost-effective triage test in men with an intermediate prior probability of CAD. The results suggest that CTCA is cost-effective over a wide range of intermediate prior probabilities of CAD in women, if the radiation exposure of CTCA is reduced to 5 mSv.
Candidate for the Lee B. Lusted Student Prize Competition