Evaluation of patients referred following cystic fibrosis newborn screening: Four year experience of a single-center

Objective: Cystic fibrosis (CF) is an inherited disorder which has negative impact on life span and quality. Newborn screening (NBS) is carried out by sweat chloride test (SCT) in babies with high immunoreactive trypsinogen (IRT) values. We aimed to present our data consisting of application and evaluation of sweat chloride test in babies referred to our center with two elevated IRT levels following national NBS. Material and Methods: This retrospective study evaluated clinical data, sweat chloride test and CF transmembrane regulator (CFTR) gene mutation analysis results of referred infants due to positive CF NBS between January 2015– January 2019. Sweat chloride test results were interpreted as normal (<30mmol/L), intermediate (30-59 mmol/L) or high (≥60mmol/L). Infants missing a second test despite an initial invalid result (<10 mmol/L) or inadequate sweat collection were not included. Results: The study group consisted of 184 infants of female/male ratio as 113/71(61.4/38.6%). The median admission time was postnatal 26 (9-98) days. The mean gestational week was 39 ± 1.75 weeks and mean birth weight was 3300 ± 432 grams. All infants passed their first stool in 48 hours at most. Five infants (3.6%) faced prolonged jaundice and two (1.4%) had neonatal pneumonia. Weight gain was insufficient in seven (5%) infants. No infant showed physical examination findings consistent with CF. First SCT was normal (n=153, 83.1%), intermediate (n=9, 4.9%) or high (n=1, 0.5%). Thirty-one infants had the second test because of inadequate sweat collection, invalid or high/intermediate range initial result. Consequently, 178 infants (96.7%) reflected normal results. Repeated SCT was high (n=2, 1.1%)/ intermediate (n=4, 2.2%) in six (3.3%) infants. CFTR mutation analysis revealed one homozygote F508 deletion and three 5T/7T/9T polymorphisms. Three patients received treatment while three were conservatively followed-up. Conclusion: NBS can provide early diagnosis of patients with CF if standardized implementation and careful interpretation of sweat chloride test are achieved. Sharing of data by centers performing sweat chloride test is extremely important for the assurance of interoperability of the system