Sweat Chloride Testing in Infants Identified as Heterozygote Carriers by Newborn Screening

The reference ranges for sweat [C1⁻] were reevaluated in 300 infants referred to our Center as carriers of at least 1 cystic fibrosis mutation identified through newborn screening. The recommended borderline range of 30 to 59 mmol/L failed to identify all individuals who were compound heterozygotes. Our data support using a borderline range of 24 to 59 mmol/L.

Abbreviations: CF NBS, Cystic Fibrosis Newborn Screening, [Cl⁻], Chloride concentration, SUNY, State University of New York, NYS, New York State, CFTR, Cystic Fibrosis Transmembrane Conductance Regulator, SD, Standard deviation, TG, Thymidine/Guanine, IVS8 5T, 5T sequence variant in intron 8