A literature review of assumptions on test characteristics and adherence in economic evaluations of colonoscopy and CT-colonography screening.

Colorectal cancer screening is an effective public health strategy for decreasing colorectal cancer mortality. Since many screening modalities exist, it needs to be determined what the most cost-effective strategy is. The aim of this review is to summarise the available cost-effectiveness evidence for colonoscopy versus CT-colonography screening, and to pay special attention to assumptions regarding test characteristics and adherence. A literature search resulted in twelve economic evaluations that could be included in the review. The incremental cost-effectiveness ratios of colonoscopy and CT-colonography versus no screening remained under 20,000 euro and 30,000 euro per life year gained, respectively. Although, both screening modalities were cost-effective according to most international thresholds, in most of the economic evaluations colonoscopy seemed more cost-effective than colonography screening. In many studies, model assumptions on major parameters (e.g. screening uptake) were more positive than real life data suggest. None of the models included indirect costs, which disproportionally favoured the relative cost-effectiveness of colonoscopy. For a good comparison of both screening methods, it is necessary that the assumptions used in economic evaluations are realistic, and include all costs.