To the Editor: Two recent publications have described programs of carrier testing for cystic fibrosis (CF) gene mutations.1,2 The authors conclude that CF carrier testing of women in early pregnancy and their partners, as well as couples contemplating pregnancy, can successfully identify those who are at risk of having a child with CF and provide them with reproductive choices. The authors use these proof-of-concept studies, in the absence of Australian economic data, to call for all couples to be offered CF carrier testing that is supported by government funding.

Although reproductive choice is clearly an individual’s right, what obligation does the community have regarding government funding of specific services to generate information that might assist such couples? Genetic screening policies have often been determined on the basis of technological capability, rather than through a rigorous evidence-based review process.3 Decision making should also take into account evidence of clinically effective screening programs, ethical principles, and opportunity costs, given the limited resources available in the health sector.

A simple economic analysis of these publications highlights some issues that need to be addressed. Massie and colleagues identified nine carrier couples by screening 3200 individuals (3000 females) before conception or during early pregnancy (CF carrier frequency, one in 30). Two of the nine carrier couples had affected pregnancies, which equates to a cost of $300 000 per CF case. In Christie and colleagues’ dataset of 1000 individuals, 73% had no family history of CF; 27 of these individuals carried CF mutations, and two carrier couples but no affected pregnancies were identified. Based on population gene frequency statistics (CF carrier frequency, one in 25; 75% of CF gene mutations being p.F508del),1 Massie et al’s screening model2 would, on average, require 3585 women to be screened to detect one affected pregnancy, costing about $740 000. Christie et al’s expanded one-step model1 would require about 3763 couples to be screened to detect one affected pregnancy, at a cost of more than $430 000. Among the 270 individuals with a family history of CF who were screened in the latter model, 126 were carriers of CF mutations (carrier frequency, one in two). It is clear that cascade screening of those with a family history would be a more effective strategy.

There is an ethical argument that projected economic benefits from the termination of affected fetuses should not play a role in decisions to offer testing.4 Nevertheless, technological capability needs to be considered together with evidence of cost-effectiveness and community acceptance before public funding of community CF carrier screening can be justified.

In reply: Our aims in publishing the outcomes of offering cystic fibrosis (CF) carrier testing to couples were to demonstrate the high acceptability rate and report the reproductive choices made by high-risk couples. Not all decisions resulted in termination.

O’Leary and colleagues rightly raise the question of screening costs. Laboratory costs will reduce with economies of scale and centralisation of testing. The recent release of a position paper on population screening for CF by the Human Genetics Society of Australasia1 will influence the demand for testing. It recommends that all couples intending to have children, and women in early pregnancy and their partners, be made aware of the availability of CF carrier testing, and that couples should be offered testing for 10 CF transmembrane conductance regulator gene mutations using an expanded one-step or two-step model.

O’Leary and colleagues suggest that cascade testing of those with a family history of CF would be a more effective strategy. However, only 10% of children born with CF have a family history.2 Studies have demonstrated that costs of CF screening are less than the averted medical care costs associated with fewer births of infants with CF.3-5 Although economic considerations are important, these should not form the primary goal of any screening program.