Purpose: Stenting of the arteria carotis interna (CAS) for treatment of carotid stenosis is increasingly applied. Costs of stents are high and conclusive trials to provide evidence on the (cost-) effectiveness of CAS as compared to carotid endarterectomy (CEA) have not yet finalized. The only evidence from a relatively small clinical trial did not show improved effectiveness of CAS compared to CEA. In contradiction, more recent published results obtained from surveys and registries indicate substantial clinical benefits for CAS. To enable estimation of the value of additional clinical trials, a value of information analysis was performed using the outcome of an expert opinion assessment which provided a quantitative estimate by specialists in the field of currently available evidence.

Method(s): An expert opinion survey was sent to members of the European endovascular network requesting point estimates and uncertainty margins for expected procedural complication rates. The expert opinion responses were combined into one (unweighted) overall expert opinion and used in a Markov model that describes patient health following carotid revascularisation. Model parameters are based on actual trial data, published complication rates for CEA and collected cost data. The model enables evaluation of the cost effectiveness of CAS compared to CEA and was used to evaluate the value of information of procedural complication rates.

Results: The survey response was low (only 11%, representing 12 experts) and the estimates provided by the experts varied considerably, reflecting the uncertainty with respect to the expected procedural complication rates. As a result, the combined expert opinion shows a large uncertainty range which encloses all complication rates found in literature. Whereas the EVPI of procedural complication rates for the most favourable and largest published series of complication rates for CAS is no more than $30 per procedure, the EVPI based on the expert opinion estimates is $2000.

Conclusions: Although performing an expert judgement assessment involves a significant amount of work and still provides a subjective rather than an objective interpretation of the available evidence, its use and subsequent value of information analysis is feasible and provides an elegant expert based quantification of the value of information.