Four-year evaluation of neonatal cystic fibrosis screening in Southern Belgium

Newborn screening for cystic fibrosis (CF-NBS) using an IRT-DNA algorithm with a 12 CFTR-variant panel and an IRT/IRT failsafe was officially implemented in the French-speaking Community of Belgium in January 2020. This screening protocol was evaluated after 4 years according to the criteria defined by the European Cystic Fibrosis Society's working group on neonatal screening. Immunoreactive trypsinogen concentration (IRT) was measured on dried blood spots collected between the second and the fourth day of life. CFTR variants genotyping was initiated when IRT ≥ 99th percentile (P99). If at least 1 variant was identified, the child was referred to a CF center for a sweat test (ST). If IRT ≥ 99.9th percentile with no variant identified, a failsafe was provided with IRT repeated on day 21 and subsequent ST in case of persistent IRT > P99. Extensive Gene Analysis was initiated if sweat chloride level was ≥ 30 mmol/L. Over a period of 4 years, 212.979 newborns were screened. Forty-two were diagnosed with CF: 34 by CF-NBS, 3 following a meconium ileus, 3 by family history and 2 missed cases. Additionally, 112 healthy carriers and 14 CFSPID were identified. The median age at the first consultation was 23 days. The sensitivity of our CF-NBS is 95% (target ≥ 95%), the positive predictive value 18% (target ≥ 30%) and CF/CFSPID ratio 2.8.

Conclusion: Although follow-up is limited, this first evaluation demonstrates encouraging sensitivity and early management before one month of age.

What is known: • Newborn screening for cystic fibrosis improves the prognosis of patients.

What is new: • This article presents an initial assessment of our screening after 4 years.