The impact of population based screening for carriers of cystic fibrosis.

The purpose of the study was to evaluate the short-term effects of population based screening for carriers of cystic fibrosis. The outcome measures included perceptions of health, anxiety, and understanding of test results. Those adults aged between 18 and 45, registered with a general practice in Inner London, who accepted the offer of carrier testing, completed questionnaires before testing, upon receipt of results, and three months later. Full data were obtained from 427 with negative test results and 14 carriers. Receipt of results had no effect upon perceptions of health or perceived risk of having an abnormal baby. Those receiving a positive test result were significantly more anxious upon receipt of this result. By three months, this anxiety had dissipated. While knowledge of the test improved from before to after testing, by three months there was some decay. Although the residual risk among those with a negative result of being a carrier was given as 1:135, at least 17% of those receiving a negative result incorrectly believed that they were at no risk of having a child with cystic fibrosis. Five of the 14 receiving a positive result erroneously believed that their results meant that they probably, but not definitely, carried the gene for cystic fibrosis. In the longer term the greatest problem of population screening would appear to be one of false reassurance rather than anxiety. Longer term studies are needed to determine how well carrier status information is retained, and how carriers and carrier couples plan and respond to pregnancy and how much understanding they retain of their test results.