Neonatal screening for cystic fibrosis: Comparing the performances of IRT/DNA and IRT/PAP

BackgroundFrench health authorities promoted a study on 553,167 newborns comparing the performances of IRT/DNA and IRT/PAP for CF newborn screening.MethodsIn parallel to IRT/DNA, PAP was assayed in newborns with IRT > 50 μg/L. Provisional PAP cutoffs at 3.0 μg/L when 50 < IRT < 100 μg/L and 1.7 μg/L when IRT > 100 were used. Positive newborns were subjected to sweat test. Optimal cutoffs were established by a non-inferiority method.Results95 CF newborns were identified (83 classical forms (ClF), including 9 meconium ileus (MI), and 12 atypical (mild) forms (AF) Of them, IRT/DNA identified 85 (73 ClF including 5 MI and 12 AF). PAP cutoffs at 1.8 μg/L when 50< IRT<100 μg/L and 0.6 μg/L when IRT>100 μg/L would identify 82 CF: 77 ClF, including 8 MI, and 5 AF. The number of sweat tests was 314 and 1039 in the IRT/DNA and IRT/PAP strategies, respectively.ConclusionsUsing the optimal cutoffs, the sensitivity of the IRT/PAP strategy would not be inferior to that of IRT/DNA if identification of MF is not required.