80 Chapter 4 Results In this population of 75 patients, 58 patients harbored 65 aneurysms: 52 patients with one aneurysm, five patients with two aneurysms and one patient with three aneurysms. Forty-three of the 58 CEMRA studies that were studied by the two observers were regarded as of good quality, eight as moderate and seven as poor. Forty of the aneurysms measured on the CEMRA images were small (less than 5 mm in diameter), 20 were of medium size (between 5 and 15 mm) and five were large (between 15 and 25 mm). There were no giant (>25 mm) aneurysms. Results for prediction of coilability of the 65 aneurysms are given in Table 1. Table 1. Coilability of all 65 aneurysms Coilable? (DSA) no yes Total Coilable? no 24 6 30 (CEMRA) yes 3 32 35 Total 27 38 65 Sensitivity of CEMRA for prediction of coilability was 84.2% (95% confidence interval (CI) 72.6 – 95.8%) and specificity was 88.9% (95% CI 77.0 – 100%). Negative predictive value (NPV) and positive predictive value (PPV) were 80% (95% CI 65.7 – 94.3%) and 91.4% (95% CI 82.1 – 100%) respectively. In 37 patients harboring 40 of the 65 aneurysms (61.5%) the observers had been confident enough about their prediction of coilability by CEMRA to state that no additional DSA was needed. For 21 patients harboring 25 of the 65 aneurysms (38.5%) access to the DSA study of the aneurysm was considered necessary before a definite decision on coilability could be made. If in this last group a decision were to be made solely on the CEMRA images, five of the 15 coil able aneurysms would have been judged as not coilable, and of the ten aneurysms which were not coilable, two would have been considered coilable (Table 2). Table 2. Coilability of the aneurysms for which an additional DSA was requested by the observers. Coilable? (DSA) no yes Total Coilable? no 8 5 13 (CEMRA) yes 2 10 12 Total 10 15 25 The cost of an MRA study as calculated from the Dutch reimbursement system20 is € 252, and for a diagnostic DSA study the cost is € 725. The total ‘diagnostic costs’ for the 75 patients in Scenario 1 is 75 x € 725 = € 54,375. For Scenario 2 this would be 75 x € 252 + 16 x € 725 = € 30,500. For Scenario 3 the costs amount to 75 x € 252 + 37 x € 725 = € 45,725 and for Scenario 4 the costs are 75 x € 252 + 29 x € 725 = € 39,925 (see Table 3).
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