The pancreatitis-associated protein (PAP). A new candidate for neonatal screening of cystic fibrosis.

Neonatal screening of cystic fibrosis (CF) is presently based on immunoreactive trypsin (IRT) assay in blood spots, whose low specificity is a matter of concern. Because the pancreatitis-associated protein (PAP) proved to be a better serum marker of pancreatic alteration than exocrine enzymes, it might be an interesting alternative for CF screening. We report here a preliminary evaluation of the PAP test, conducted in retrospect on blood spots from groups of neonates already screened for CF with the IRT. Neonates with elevated IRT were submitted to subsequent analysis of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. Neonates with normal IRT (n = 990) or high IRT but normal genotype (n = 28) had normal PAP. Elevated PAP was observed in all CF neonates (n = 11). False-positives for the PAP test were found only among neonates with high IRT and heterozygotes for a mutation in the CFTR gene (6 out of 17 cases). That group represents less than 0.2% of newborns. These results therefore suggest that PAP discriminates CF neonates with a significantly better specificity than IRT.