Sweat testing in newborns positive to neonatal screening for cystic fibrosis.

Sweat chloride concentrations above 40 mmol/l are unusual in newborns screened for cystic fibrosis and should be followed up. Centiles of sweat chloride concentrations in newborns positive to cystic fibrosis neonatal screening are presented. There are no significant correlations between age at sweat testing and sweat chloride concentration or quantity of sweat collected.