Effect of salt supplementation on the rate of inadequate Sweat collection for infants less than 3 months of age referred for the Sweat test

Background: Sweat testing in young infants (≤ 3 months) with a positive newborn screen for Cystic Fibrosis (CF) can yield higher rates of inadequate sweat collection. The role of salt supplements in improving sweat collection has not been studied before. Methods: All young infants referred to our CF center for sweat testing were randomized to either receive salt supplements {l/8th teaspoon salt (750 mg)} mixed in formula feeds 1 day prior to sweat testing (study group) or no salt supplement (controls). Results: Of the 151 young infants that underwent sweat testing over 18 months, 75 received salt supplements, while 76 did not. A total of 9 (11.8%) infants in the salt supplement group had inadequate sweat collection, as compared to 4 (5.2%) infants in the control group (p = 0.16, Fisher's Exact Test). Conclusions: Oral salt supplementation for young infants prior to sweat testing does not help to reduce the rates of inadequate sweat collection.