Pro's and contra's of screening asymptomatic patients for carotid stenosis. Do the benefits indeed outweigh the 'costs'?
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Stroke is a major cause of disability and handicap in Western societies. Loss in health related quality of life as well as the financial burden is considerable, which primary prevention might partly avert. Secondary prevention in symptomatic patients with high through low grade stenosis by means of carotid endarterectomy and/or pharmacotherapy was shown to be beneficial. Recent evidence indicates that also for asymptomatic patients with severe stenosis endarterectomy may be beneficial. This raises the question whether population based screening or a high risk approach is worthwhile to identify candidates for operation. Accordingly, the research question reads: 'What is the balance between costs and effects of screening, subsequent diagnostic workup and possible endarterectomy in individuals with asymptomatic carotid stenosis, as compared to the current non-intervene, respectively, medical treatment only approach'?
The domain as well as frequency of screening will affect the balance between costs and effects. Thus, two main scenarios are evaluated, i.e., periodic population screening from a certain age onward and high risk screening. The latter comprises individuals with symptomatic cardiovascular disease (CVD) in territories other than the brain or with a high cardiovascular risk profile.
A typical population based screening strategy that will be evaluated is: screening with 5 year intervals from the age of 55 years onward until the age of 75. For the high risk approach initially a similar interval will be evaluated. However, the starting age is determined by the age CVD becomes apparent, i.e, 58 years on avarage in the UMCU cohort with symptomatic disease (SMART).
To answer the questions a modelling study wil be conducted taking into account Dutch population characterstics (CBS), prevalence of asymptomatic stenosis (ERGO, Tromso, AGES-Iceland, CHS-USA, SMART), stroke incidence in asymptomatic patients before and after endarterectomy (ERGO, SMART, ACAS, ACST), incidence of diagnosis and operation related complications and the literature on the costs and QoL outcomes. An existing Markov state stroke model (Buskens, Radiology 2004) will be adapted and updated with the relevant parameters to estimate the differences in costs and effects of the screen vs no-screen scenarios. Where relevant, additional analyses on the data from the cohort studies will be performed to obtain the model parameters.
From a societal perspective and with a life-time time horizon the incrementeal cost-effectiveness (discounted by 4%) will be calculated for the Dutch setting in terms of costs per stroke avoided, costs per life year gained and costs per QALY gained.
To evaluate uncertainty univariate and multivariate sensitivity analyses (Monte Carlo simulation) will be performed.