Cost-effectiveness of CTA, MRA and DSA in patients with non-traumatic subarachnoid hemorrhage 139 In a sensitivity analysis, results remained stable also for assumption of equal treatment cost for coiling and clipping. Furthermore results remained stable for the assumption of higher costs of DSA up to factor 2.8. Higher sensitivity and specificity for detection of aneurysms and determination of feasibility of coiling for CTA and MRA up to 96% also yielded stable results. The probabilistic sensitivity analysis showed that in the base case analysis, DSA had a 98-100% probability of being cost-effective. In the scenario analysis, CTA had the highest probability of being cost-effective (91%), followed by DSA (9%) and MRA (0%). Because in the scenario analysis effectiveness is equal for all strategies, these percentages are constant over the different values of willingness to pay for a QALY. Discussion When a patient presents with a suspected ruptured intracranial aneurysm, imaging is a challenge. Due to high risk of case fatality of ruptured intracranial aneurysms, timely detection of a causative aneurysm and determination of treatment are mandatory. Based on imaging results, patients are either left untreated, clipped surgically or receive endovascular treatment. In the last decades, much research has been done on evaluating best treatment options and imaging modalities. Especially the role and necessity of DSA in this patient population is widely discussed.29-32 No paper has yet evaluated the best diagnostic pathway based on cost-effectiveness. Our paper, comparing MRA, CTA and DSA, is a contribution to this field. Our analysis is based on a one-year horizon. This holds potential conflict concerning the long term validity of the results. This matter can be addressed looking at the ISAT trial which was based on a one year’s model and validity of results was proclaimed to be stable for up to 7 years.8 Incomplete occlusion and refilling of the aneurysm is a complication occurring mainly in coiling which can cause rebleeding, resulting in a higher rate of follow up imaging costs and re-interventions in the endovascular group. The rate of recanalization is highest in the first months and decreases significantly over time.33-36 Follow-up for detection of recanalization after 6 months may not be necessary.35 Wolstenholme et al. determined cost of coiling and clipping in the first year for western countries.13 Calculation of total costs for both treatment options included not only cost for material, intensive care and standard unit days, and medication, but also cost of follow-up imaging and re-intervention for the first year. Taking the results from literature, we can assume that validity of our data will be stable for the following years. Our results show that DSA is the most cost-effective imaging modality and is superior to both MRA and CTA. Although initial test costs are about three times higher than those of MRA and CTA, optimal detection of aneurysms and determination of treatment in DSA yields lower overall one year’s costs per patient and the highest QALYs. We assumed DSA to be standard of reference with sensitivity and specificity for detection and determination of treatment of 100%. In cases where coiling was performed, costs for diagnostic DSA were accounted for separately. Costs of imaging were put to €725, following the Dutch healthcare costs guideline.22 It is debatable to state that sensitivity and specificity of DSA are 100% in an acute setting.37 Also actual costs of DSA might be higher than in our model. We therefore performed sensitivity analysis showing stable results even for assumption of 80% sensitivity in aneurysm
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