Screening for cystic fibrosis Should begin with cascade screening

Abstract

EDrrOR,-Andrew N Phillips and colleagues used the CD4 lymphocyte count to predict long term survival after HIV infection in men with haemophilia,' but the biological variables that influence the CD4 count limit the applicability of their results to other risk groups-for example, homosexual men.I studied 25 HIV positive patients who had been followed up for more than six years in my clinic. Eleven were homosexual men, of whom three died of AIDS and three others developed AIDS during the follow up; one patient had a low CD4 lymphocyte count (1OOx 106/1, but the four others remained asymptomatic with counts of over 300x1061/1. Nine patients had been injecting drug users: two of these died in the sixth and seventh years after diagnosis while the rest remained asymptomatic with CD4 lymphocyte counts of over 300x 106/1 during the six years of follow up. The five other patients were either haemophilic or thought to have been infected through blood transfusion. One of these died after 10 years and one had a CD4 lymphocyte count of 50x 106/1, but the three others were asymptomatic with counts of over 500x 1061/1. carried out in the clinic at the time. This was referred to in information sent to the patients before they attended the clinic but was not specifically discussed at the booking visit. Named HIV testing was discussed with 18 of the women. Fourteen were tested, and all were negative for HIV antibodies. Of the remaining 204 women, 84 believed that they had had a named test at their first antenatal visit; 64 said that they had not been tested, and 56 were unsure. Of the 84 who believed that they had had a named test, 76 believed that the result had been negative and eight did not know their result, of whom four added the comment that it was anonymous.One hundred and eighty six patients thought that HIV infection should have been discussed. When asked whom they would like to speak to about the test for HIV antibodies 34 chose their general practitioner, 24 a midwife, 13 a specialist HIV counsellor, and nine a hospital doctor; 106 had no particular preference. One hundred and fifty five women thought that HIV testing should be compulsory.Our study highlights the widely held misconception regarding antenatal testing for HIV antibodies. Although in our unit named testing for HIV antibodies was not discussed with 92% of the patients antenatally, only one third were certain that they had not been told the result of the test. Furthermore, 90% of those who believed they had had a named test thought that their result had been negative. The anguish caused by such a misunderstanding has been commented on previously.2 Ninety three per cent of the patients did not think it necessary to discuss the issues with a specific HIV counsellor. We support this view that antenatal carers would be the appropriate people to discuss testing for HIV antibodies and believe that the introduction of specific counsellors would further "mystify" such testing.We believe that the universal offer of testing for HIV antibodies, with informed consent,...

Results of Duchenne muscular dystrophy family screening in practice: leaks rather than cascades?

“…The term ‘cascade screening’ was introduced to describe a formalised method for targeted, population screening for cystic fibrosis (5, 6, 11). This strategy was also adopted for the identification of affected individuals and carriers of another X‐linked condition, Fragile X syndrome.…”

“…Recognition of potential carriers within families provides the opportunity for genetic counselling ensuring that females are aware of their reproductive options and that appropriate cardiac investigations are offered. For over 30 years in the case of DMD and its allelic disorder Becker muscular dystrophy (BMD), many clinical genetics centres have participated in a process quite similar to what became known widely as ‘active cascade screening’(4–6) to identify the close relatives of known affected or carrier individuals to inform them of their genetic and health risks. From Netherlands, a retrospective review of an established programme of extended family screening indicated about 1 of 3 of female potential carriers at 50% risk in DMD/BMD had not been tested (7).…”

“…As well as the risk of having affected offspring, female carriers are at risk of developing cardiomyopathy and current guidelines recommend five-yearly cardiac surveillance (3). For over 30 years in the case of DMD and its allelic disorder Becker muscular dystrophy (BMD), many clinical genetics centres have participated in a process quite similar to what became known widely as 'active cascade screening' (4)(5)(6) to identify the close relatives of known affected or carrier individuals to inform them of their genetic and health risks. For over 30 years in the case of DMD and its allelic disorder Becker muscular dystrophy (BMD), many clinical genetics centres have participated in a process quite similar to what became known widely as 'active cascade screening' (4)(5)(6) to identify the close relatives of known affected or carrier individuals to inform them of their genetic and health risks.…”

Estimating the Efficacy and Efficiency of Cascade Genetic Screening

“…One offers testing to the population at large; the other targets relatives of carriers previously identified through the testing of their phenotypes or genotypes. The latter strategy, which has been most intensively assessed for cystic fibrosis (Holloway and Brock 1994;Marteau 1994;Super et al 1994aSuper et al , 1994b, is usually referred to as "cascade screening." The major difference between population and cascade screening lies in the design of the educational component.…”