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Both the US National Institutes of Health and a Health Technology Assessment review in the UK have recommended the introduction of population antenatal screening of prospective parents for cystic fibrosis carrier status (see Cystic fibrosis summary for more information). These recommendations have not met with universal approval. Among the unanswered questions is the best screening method: couple screening, in which both parents supply a sample at the same time, and two-step screening, in which only the mother supplies a sample initially and her partner supplies a sample for testing if she proves positive. One of the criteria for a successful screening programme is accurate recall of risk status by the people who are tested. Marteau et al have surveyed couples participating in trial screening programmes to see whether those who tested negative accurately recalled their residual risk three years later [Marteau, T.M. et al. (1999) Am J Obstet Gynecol 181, 165-169 (Abstract)]. They found that those who underwent couple testing were 4.5 times more likely to recall accurately that they were unlikely (rather than definitely, likely, definitely not, or don't know) to be CF carriers. The authors suggest that the best approach from the psychosocial point of view is complete couple screening and with full disclosure of results, that is, samples are taken from both parents at the same time, both are tested, and both parents are told their result. This differs from the usual method of couple screening, in which the father's sample is taken at the same time as the mother's but only tested if the mother's is positive. Couple screening avoids the anxiety that results from the couple having to wait for the father's test result if the mother has been told that her test is positive.

Comment: The approach to screening is an important parameter because it affects both the financial and the human costs. The approach suggested by Marteau et al would substantially increase the financial cost of the screening programme, as the single most important factor in determining cost is the cost of the DNA test itself, and such tests would have to be performed on both partners of every couple who accepted the offer of antenatal testing, rather than on all mothers and only approximately 5% of fathers (that is, the partners of the 5% of women who tested positive). These costs would probably prove prohibitive. Marteau et al's approach would, however, seem to involve the lowest human costs, both in terms of anxiety, and accuracy of recall of the meaning of the test result. It would also mean that if either parent were involved in a subsequent pregnancy, he or she would not need to be re-tested.