Factors Affecting Immunoreactive Trypsinogen Levels in Cystic Fibrosis Newborn Screening.

OBJECTIVE

Cystic fibrosis (CF) is a genetic disorder associated with high morbidity and mortality. Elevated immunoreactive trypsinogen (IRT) levels are used for CF newborn screening (NBS). This study aims to identify factors contributing to elevated IRT levels.

MATERIALS AND

METHODS

This case-control study included children with false-positive IRT levels (Group 1) detected during CF NBS between January 1, 2023, and January 1, 2024. A control group (Group 2) consisted of healthy children with normal IRT levels. Demographic and clinical data were retrospectively collected and compared between the 2 groups.

RESULTS

A total of 76 infants with elevated IRT were identified, of whom 3 were excluded due to a confirmed CF diagnosis. Consequently, 73 infants were included in Group 1 and 77 in Group 2. The median age at admission was significantly lower in Group 1 (P < .001). No significant differences were observed between the groups regarding sex, growth Z-scores, daily weight gain, or season of birth (P > .05). Maternal factors, including higher gravity (P=.013), smoking exposure (P=.023), and chronic diseases (P=.003), were more common in Group 1. Logistic regression analysis identified gestational age <42 weeks and maternal chronic disease (P < .001, P =.006) as independent predictors of elevated IRT.

CONCLUSION

False positives are common in IRT-based NBS. Factors such as gestational age and maternal characteristics-including higher gravity, smoking exposure, and chronic illnesses-may be linked to elevated IRT levels in newborns. Post-term birth may protect against false-positive IRT. Perinatal and maternal factors should be considered when interpreting IRT results to improve screening accuracy.