Background and Objective: The cost-effectiveness of clinical interventions is often assessed using current care as the comparator, with national guidelines as a proxy. However, this comparison is inadequate when clinical practice differs from guidelines, or when clinical practice differs between hospitals. We examined the degree of variation in the way patients with a recent transient ischemic attack (TIA) or minor ischemic stroke are assessed and used the results to illustrate the importance of investigating possible clinical practice variation, and the need to perform hospital-level cost-effectiveness analyses (CEAs) when variation exists.
Methods: Semi-structured interviews were conducted with 16 vascular neurologists in hospitals throughout the Netherlands. Questions were asked about the use of initial and confirmatory diagnostic imaging tests to assess carotid stenosis in patients with a recent TIA or minor ischemic stroke, criteria to perform confirmatory tests, and criteria for treatment. We also performed hospital-level CEAs to illustrate the consequences of the observed diagnostic strategies in which the diagnostic test costs, sensitivity and specified were varied according to the local hospital conditions.
Results: 56 % (9/16) of the emergency units and 63 % (10/16) of the outpatient clinics use the initial and confirmatory diagnostic tests to assess carotid stenosis in accordance with the national guidelines. Of the hospitals studied, only one uses the recommended criteria for use of a confirmatory test, 38 % (6/16) follow the guidelines for treatment. The most cost-effective diagnostic test strategy differs between hospitals.
Conclusions: If important practice variation exists, hospital-level CEAs should be performed. These CEAs should include an assessment of the feasibility and costs of switching to a different strategy.

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Journal Applied Health Economics and Health Policy
Buisman, L.R, Rijnsburger, A.J, den Hertog, H.M, van der Lugt, A, & Redekop, W.K. (2016). Clinical Practice Variation Needs to be Considered in Cost-Effectiveness Analyses. Applied Health Economics and Health Policy, 14(1), 67–75. doi:10.1007/s40258-015-0167-4