28 Chapter 1 patients with a history of aneurysm coiling are more anxious or depressed than the general population461 which is not alleviated by a reassuring outcome of the follow-up study. Cost-effectiveness Evaluations of diagnostic strategies cannot be complete without cost-effectiveness analyses.462-464 In the various schemes used to describe the requisites for complete assessment of a diagnostic method, cost- effectiveness always is the completing last step.462,463,465,466 Cost-effectiveness studies compute a cost per unit of effect measured. Any diagnostic test characteristic can be used as an output parameter: for example, cost per surgery avoided, cost per appropriately treated patient, cost per life-year gained, or cost per quality adjusted life year (QALY).462 Different models can be used, but the validity of the model’s input parameters is crucial for its credibility. The validity of all input variables must be based on solid evidence from literature or, when such evidence is lacking, any uncertainties pertaining to the value of the different parameters should be incorporated into the model. The Markov model, where a patient can go from one defined health state to another based on several interventions or decisions, is often used.467-469 The Monte Carlo method incorporates a degree of uncertainty into the Markov model in order to simulate the outcomes for a larger group of patients.470 In the setting of SAH diagnosis and treatment, different facets can be evaluated in cost-effectiveness analyses. Most cost-effectiveness studies to date have focused on treatment. Thus studies assessing general costs of treatment,471 and whom to treat472-476 which treatment to use,477-486 and where to treat487 have been published in the literature. Only two studies assessed cost-effectiveness of screening for aneurysms. The first concerned MRA in patients with a positive family history for aneurysms, and concluded that screening in this particular group was recommended with a cost-effectiveness threshold of €20,000/QALY.488 The other study concerned CTA in patients who had suffered a SAH and had been clipped in the past. The authors concluded that screening in this group is not recommended from a cost- effectiveness perspective.489 Cost-effectiveness studies comparing different imaging modalities in patients with aneurysmal SAH hardly exist. One study compared DSA and MRA in the follow-up of coiled aneurysms and concluded that MRA provided equivalent health benefits compared to DSA, and was cost-saving.490 We performed a cost-effectiveness analysis comparing three different imaging modalities - CEMRA, CTA and DSA - in patients with a SAH, and tested different scenarios in a Markov decision model. The data presented in Chapters 2 and 3 were used as input parameters in the model. The results of this study are described in Chapter 8: Cost-effectiveness of CTA, MRA and DSA in patients with suspected ruptured intracranial aneurysms: a decision model. In cost-effectiveness studies, all steps in evaluating diagnostic tests in patients with an aneurysmal SAH are addressed, whether it be the hierarchical steps as described by Fryback465 (1.Technical efficacy, 2. Diagnostic accuracy, 3. Impact on diagnostic reasoning, 4. Impact on patient management, 5. Impact on patient outcome, 6. Cost-effectiveness), or those in the stepwise approach by Van den Bruel462 (1.
proefschrit Van Zwam inhoud met kaft en stellingen.indd
To see the actual publication please follow the link above