Planning the development of cystic fibrosis gene carrier screening

It is now possible to test individuals to assess their cystic fibrosis gene carrier status and a range of strategies for screening the population have been piloted. The objective of this research was to develop a planning framework which health care planners and purchasers can use to assess the overall quantifiable outcomes and direct costs resulting from a year of alternative screening strategies and the ways costs and outcomes evolve over time. Beyond broader ethical and clinical considerations the information provided by such a framework is needed to support decisions surrounding the development of screening programmes.

Operational Research modelling techniques were used to develop the planning framework. To help illustrate the framework it was then used to assess the quantifiable outcomes and direct costs of three of the main alternative screening strategies: from antenatal clinics, '2-step' screening where females are tested first followed by a screening invitation to the partners of female carriers, and 'couple' screening where both partners must agree to be tested at the outset; and from primary practice clinics 'active' contact of attenders. Quantifiable outcomes are defined as the number of individuals informed of their carrier status and the number of carriers, carrier couples, and affected fetuses detected. Direct costs are those associated with the recruitment and testing of individuals and the subsequent counselling of any gene carriers or carrier couples identified. Results are based on services for a resident population of 250,000 at two time points, year one and a year at 'steady state'.

The resultant framework estimates the number of individuals tested using data on the size of the target population, the proportion of that population alerted to the screening service, and the proportion who agree to be tested when approached. Given service users, prevalence data are used to assess service outcomes. Given the number of individuals approached and the subsequent demands for services, service costs can be estimated. Preliminary results indicate that in the short-term health care purchasers and planners who favour screening are likely to opt for antenatal strategies. Although the high coverage of the primary practice strategy leads to high outcomes in year one, relative to the antenatal strategies, it also leads to very high costs. At 'steady state', cost and outcome differences between the strategies are less marked.

This paper provides a framework which can be used to provide information to support decision-making surrounding the development of screening services. The methodology fills an important void in the literature and complements research elsewhere by health economists and by geneticists and their research colleagues. Preliminary findings based upon use of the approach demonstrate the need for continued research to further refine and improve the methodology.