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SCREENING FOR CYSTIC FIBROSIS ASSESSED.

Now that the gene for cystic fibrosis (CF) is known, it is possible to identify carriers as well as affected neonates. However, screening strategies are imprecise, raise complex issues, and involve difficult decisions. Three studies of different screening techniques for CF provide needed information about screening programs.

A Scottish study offered prenatal CF screening to 8536 couples; 68 percent were eligible and agreed to be screened. Couples were only notified of high-risk status if both partners were carriers of the gene (yielding a 1:4 chance of having an affected child). All four high-risk couples identified chose to test their unborn fetus, and the three affected pregnancies were terminated. Anxiety among screened couples was low and 99 percent expressed satisfaction with the screening approach.

A British study tested 1563 relatives and partners of 607 people with CF. This "cascade" screening detected 15 carrier couples; of their nine pregnancies, eight had prenatal testing and three were terminated.

An Australian study screened newborns with a two-tier strategy: blood trypsinogen levels measured soon after birth, followed by direct genetic analysis in newborns with markedly elevated levels. Of 88,752 screened infants, 1004 (1.13 percent) had elevated trypsinogen. Twenty-three of these were homozygous for CF; another 69 had mutated genes (possible CF), and 6 of these had a positive sweat test. Screening thus led to the early diagnosis of CF in 29 neonates.

Comment: An editorialist notes that all three screening approaches have high specificity, thus minimizing anxiety, and adds that there may not be one preferred technique, but rather a combination of approaches to meet different community needs. Unfortunately, the study of neonatal screening did not determine whether early diagnosis of CF in infants improves outcome.

— KI Marton

Published in Journal Watch General Medicine July 8, 1994

Citation(s):

Raeburn S. Screening for carriers of cystic fibrosis: time to decide. BMJ 1994 Jun 4 308 1451-1452.

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• Medline abstract (Free)

Ranieri E et al. Neonatal screening for cystic fibrosis using immunoreactive trypsinogen and direct gene analysis: four years' experience. BMJ 1994 Jun 4 308 1469-1472.

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• Medline abstract (Free)

Super M et al. Active cascade testing for carriers of cystic fibrosis gene. BMJ 1994 Jun 4 308 1462-1468.

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Livingstone J et al. Antenatal screening for cystic fibrosis: a trial of the couple model. BMJ 1994 Jun 4 308 1459-1462.

• Original article (Subscription may be required)
• Medline abstract (Free)