A single-tube multiplex system for the simultaneous detection of 10 common cystic fibrosis mutations

Prenatal genetic testing for cystic fibrosis: a systematic review of clinical effectiveness and an ethics review

PURPOSE

We aimed to assess the clinical value of prenatal testing for cystic fibrosis (CF) and whether ethical considerations would affect endpoint selection.

METHODS

To determine effectiveness, we conducted a systematic literature review whose protocol outlined search strategies across eight databases, study inclusion criteria, and prespecified literature screening, data extraction, and synthesis processes. We conducted a scoping search on ethical considerations.

RESULTS

The genetic test showed good diagnostic performance. A change in clinical management was observed: termination of pregnancy (TOP) occurred in most cases where two pathogenic variants were identified in a fetus of carrier parents (158/167; 94.6%). The TOP rate was lower in pregnancies where CF was diagnosed after fetal echogenic bowel detection (~65%). TOP and caring for a child with CF were both associated with poor short-term parental psychological outcomes. Ethical analyses indicated that informed decisions should have been the main endpoint, rather than CF-affected births prevented.

CONCLUSION

CF testing leads to fewer CF-affected births. It is difficult to assess whether this means the test is valuable, since patients may not value TOP primarily in terms of maternal or fetal health outcomes, psychological or otherwise. The value of testing should arguably be measured in terms of improving patient autonomy rather than health.

Multiplex PCR for typing and subtyping influenza and respiratory syncytial viruses

A multiplex reverse transcription (RT)-PCR method that has been developed is capable of detecting and subtyping influenza A (H1N1 and H3N2) and B viruses as well as respiratory syncytial virus (RSV) types A and B in respiratory clinical samples taken as part of a national community-based surveillance program of influenza-like illness in England and Wales. The detection of each different pathogen depended on distinguishing five amplification products of different sizes on agarose gels following RT-PCR with multiple primer sets. The multiplex RT-PCR was tested with 65 nasopharyngeal apirates from which RSV had been isolated and 237 combined nose and throat swabs from which influenza A (H1N1 and H3N2) or B virus had been detected by virus isolation, as well as 40 respiratory samples from which other viruses including cytomegalovirus, herpes simplex virus, enteroviruses, and parainfluenza viruses had been grown. For the typing and subtyping of influenza A and B viruses and RSV types A and B, the multiplex RT-PCR gave an excellent (100%) correlation with the results of conventional typing and subtyping with specific antisera. Multiplex RT-PCR can also be used to accurately detect more than one viral template in the same reaction mixture, allowing viral coinfections to be identified with the same respiratory specimen.

P67L: a cystic fibrosis allele with mild effects found at high frequency in the Scottish population

Only three mutant cystic fibrosis (CF) alleles have to date been established as conferring a dominant mild effect on affected subjects who are compound heterozygotes. We now add a fourth, P67L, which occurs on about 1.4% of Scottish CF chromosomes. Among 13 patients (12 unrelated) with this allele, the average age at diagnosis was 22.5 +/- 11.3 years. None of the cases had consistently raised sweat chloride concentrations, the average value being 57 +/- 9 mmol/l; 77% of the patients were pancreatic sufficient. When compared to three other established mild CF alleles, R117H, A455E, and 3849 + 10kb C-T, a compound heterozygote for P67L has minimal disease and clinical suspicions are unlikely to be confirmed other than by DNA typing.

The incidence of cystic fibrosis in Scotland calculated from heterozygote frequencies

The incidence of cystic fibrosis (CF) has previously been calculated from epidemiological surveys and from neonatal screening. With the cloning of the CF gene it has become possible to derive incidence figures from heterozygote frequencies, provided that the distribution of mutant alleles among healthy carriers is the same as among affected people. We have estimated the allele frequencies for four CF mutations, AF508, G551D, G542X and R117H, in 14360 unselected women undergoing antenatal heterozygote screening. The proportion of R117H, an allele of known mild effect, was much greater for heterozygotes than for homozygotes. The incidence of CF was therefore calculated from the heterozygote frequencies of AF508, G551D and G542X in a larger cohort of 27 161 successively screened women. The point estimate for the incidence of CF in the Scottish population was 1 in 1984, with 95% confidence intervals of 1 in 1692 to 1 in 2336.