[Evaluation of diagnosis and follow-up in screened children with cystic fibrosis in Normandy]

Newborn screening for CF in France: An exemplary national experience

Newborn screening (NBS) for cystic fibrosis (CF) was implemented throughout France since 2002, with a 3-tiered strategy consisting in an immunoreactive trypsinogen (IRT) measurement at day-3, a search for the most common mutations responsible for CF when the IRT value is above the cut-off level, and, if necessary, a safetynet retesting of IRT at day-21. Coordination and follow-up are ensured at the national level and NBS is carried out through a regional organization involving NBS centers, biochemical and molecular genetics laboratories. Sweat testing and comprehensive mutation gene analysis are then performed according to a defined algorithm. Between 2002 and 2014, screening for the 30 most common mutations identified 87% of the alleles and comprehensive mutation gene analysis performed when applicable identified more than 300 additional mutations and resulted in a detection rate of 99.8% of the mutated alleles. Program surveillance ensured at a national level allowed to carry out adaptation of cut-off levels and removal of the p.Arg117His mutation. Thanks to these modifications, the performance of the French NBS program for CF meets the European guideline standards regarding positive predictive values, sensitivity and time to initial visit at the CF center, thus making the strategy effective. © 2020 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Cystic fibrosis in Tunisian children: a review of 32 children

Background

Cystic fibrosis is rare in Tunisia. Its diagnosis requires experienced specialists. Its prognosis is poor in developing countries.

Objectives

To study the epidemiologic, clinical, genetic features and the therapeutic challenges of cystic fibrosis in Tunisian children.

Methods

Covering a period of 21 years, this retrospective study included all patients with a definite diagnosis of cystic fibrosis from the Pediatrics Department B of The Children's Hospital of Tunis.

Results

Data from 32 children (14 boys and 18 girls) were collected. The diagnosis was made during the first year of life in 28 cases. Meconium ileus was found in 5 cases, respiratory manifestations in 22 cases, chronic diarrhea in 19 cases, faltering growth in 17 cases and a pseudo Barter syndrome in 2 cases. The sweat chloride test was positive in all cases. The most frequent mutation was F508del (56% of cases). Respiratory complications marked the outcome. Among our 32 patients, 15 patients (50%) died at an average age of 5 years and 3 months, mainly due to respiratory failure. The mean age of the surviving patients was 5 years.

Conclusion

Cystic fibrosis prognosis is poor in our series compared to developed countries due to the longer diagnostic delay and the limited therapeutic options.

Variants in Solute Carrier SLC26A9 Modify Prenatal Exocrine Pancreatic Damage in Cystic Fibrosis

OBJECTIVES

To test the hypothesis that multiple constituents of the apical plasma membrane residing alongside the causal cystic fibrosis (CF) transmembrane conductance regulator protein, including known CF modifiers SLC26A9, SLC6A14, and SLC9A3, would be associated with prenatal exocrine pancreatic damage as measured by newborn screened (NBS) immunoreactive trypsinogen (IRT) levels.

STUDY DESIGN

NBS IRT measures and genome-wide genotype data were available on 111 subjects from Colorado, 37 subjects from Wisconsin, and 80 subjects from France. Multiple linear regression was used to determine whether any of 8 single nucleotide polymorphisms (SNPs) in SLC26A9, SLC6A14, and SLC9A3 were associated with IRT and whether other constituents of the apical plasma membrane contributed to IRT.

RESULTS

In the Colorado sample, 3 SLC26A9 SNPs were associated with NBS IRT (min P=1.16×10(-3); rs7512462), but no SLC6A14 or SLC9A3 SNPs were associated (P>.05). The rs7512462 association replicated in the Wisconsin sample (P=.03) but not in the French sample (P=.76). Furthermore, rs7512462 was the top-ranked apical membrane constituent in the combined Colorado and Wisconsin sample.

CONCLUSIONS

NBS IRT is a biomarker of prenatal exocrine pancreatic disease in patients with CF, and a SNP in SLC26A9 accounts for significant IRT variability. This work suggests SLC26A9 as a potential therapeutic target to ameliorate exocrine pancreatic disease.

[The French nationwide cystic fibrosis newborn screening program: strategy and results]

In 2002 France implemented a nationwide newborn screening program for cystic fibrosis (CF). The strategy combined immunoreactive trypsinogen and, in case of a value over the cut-off level, DNA analysis in dried blood samples at day 3. Data were centralized and periodically analyzed thus maintaining the percentage of samples requiring mutation analysis (0.6%), limiting the number of false-positive cases (0.1%) without increasing the number of false-negative cases (3.2%). 3.527.353 infants were screened between 2002 and 2006. The overall cystic fibrosis incidence was 1/ 4136 with a wide range of regional variations. Dilemma case presentation occurred for 14 % of the patients; an European working group is actively working on this topic, attempting to establish a consensus on the adequate procedures. Cystic fibrosis newborn screening is feasible all over a nation but needs a strong organization from maternity wards to CF care centers.

Implementation of the French nationwide cystic fibrosis newborn screening program

OBJECTIVES

To describe optimization of a nationwide newborn screening program for cystic fibrosis (CF) that combines an immunoreactive trypsinogen (IRT) assay and DNA mutation analysis in dried blood samples at day 3.

STUDY DESIGN

Data from regional screening laboratories and CF care centers were centralized and periodically analyzed to allow adaptation, thus limiting the number of false-positive cases.

RESULTS

A total of 2717905 infants were screened between 2002 and 2005. Flow chart protocol was modified twice. First, the IRT d3 cutoff value increased from 60 to 65 microg/L, thus decreasing the percentage of samples requiring mutation analysis from 0.82% to 0.64%. Second, for infants with no mutations using the screening panel, a recall for IRT was performed only if IRT d3 was > 100 microg/L; the percentage of recalls decreased from 0.51% to 0.12%, and the percentage of infants requiring a sweat test decreased from 0.14% to 0.01%. No significant change in the CF detection rate was observed after these 2 modifications. A total of 625 CF cases were detected, and 22 false-negative findings (3.4%) were observed, most of them inevitable, with a low initial IRT.

CONCLUSIONS

The centralized data analysis led to changes in the screening strategy to optimise the newborn screening program.