Comparison between two newborn screening strategies for cystic fibrosis in Argentina: IRT/IRT vs. IRT/PAP.

BACKGROUND The benefits ofearlycystic fibrosis (CF) detectionusing newborn screening (NBS)has ledto widespread use in NBSprograms. Since 2002, a two-stageimmunoreactive trypsinogen(IRT/IRT)screening strategy has been used as aCFNBS method in all public maternity unitsin the City of Buenos Aires, Argentina. However, novel screening strategies may be more efficient. The aim of this study is to prospectively compare two CFNBS strategies:IRT/IRTandIRT/PAP(pancreatitis-associated protein). METHODS Atwo-year prospective study was performed.IRT was measuredin dried blood samples collected 48-72 hours after birth. Whenan IRT value was abnormal, PAP was determined, and a second visit was scheduled to obtainanother sample for IRTbefore 25 days of life. Newborns with a positive CFNBS were referred for confirmatory sweat test. RESULTS There were 69,827 births in the City of Buenos Aires during the period studied; 918 (1.31%) had an abnormal IRT. A total of 207 children (22.5%) failed to return for the second IRT, but only two PAP (0.2%) were not performed.IRT/IRT was more likely to lead to a referral for sweat testing than IRT/PAP (OR 2.3 [95% CI 1.8, 2.9], p<0.001). Sensitivity and specificity were: 80% and 100% and 86.5% and 82.6%for IRT/IRT and IRT/PAP strategies, respectively. CONCLUSION The IRT/PAP strategy is more sensitive thanIRT/IRT and has similar specificity; it avoids a second visit and unnecessary sweat testing, and it reduces loss to follow-up in our population. This article is protected by copyright. All rights reserved.