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Quantity not sufficient rates and delays in sweat testing in US infants with cystic fibrosis
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  • Susanna McColley,
  • Alexander Elbert,
  • Runyu Wu,
  • Clement Ren,
  • Marci Sontag,
  • V. Legrys
Susanna McColley
Ann & Robert H.Lurie Children's Hospital of Chicago
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Alexander Elbert
Cystic Fibrosis Foundation
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Runyu Wu
Cystic Fibrosis Foundation
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Clement Ren
Indiana University System
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Marci Sontag
CI International
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V. Legrys
UNC
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Peer review status:UNDER REVIEW

03 Jun 2020Submitted to Pediatric Pulmonology
04 Jun 2020Assigned to Editor
04 Jun 2020Submission Checks Completed
06 Jun 2020Reviewer(s) Assigned

Abstract

Background: Diagnostic sweat testing is required for infants with positive newborn screening (NBS) tests for cystic fibrosis (CF). Infants have “quantity not sufficient” (QNS) sweat volumes more often than older children. A comprehensive study of QNS sweat volumes in infants has not previously been reported. Methods: We surveyed US CF Centers to obtain QNS rates in all infants who had sweat testing at < 14 days and < 3 months of age. We then calculated QNS rates reported to the Cystic Fibrosis Foundation Patient Registry (CFFPR) 2010-2018 in 10-day increments from 1 to 60 days of life. We compared QNS sweat tests rates in preterm (< 37 weeks gestational age) versus term infants. We assessed age at sweat test and proportion of infants who did not have a sweat test reported by 60 days of age. Results: Thirty-nine of 144 (27%) of CF Centers reported a mean QNS rate of 10.5 % (range, 0-100) in infants < 14 days old. CFFPR data showed highest QNS rates in the youngest infants and in those born < 37 weeks gestation. The median age at sweat testing decreased over time, but > 22% of infants did not have a sweat test reported by 60 days. Conclusion: Higher QNS rates are seen in the youngest infants with CF, but > 80% of infants < 2 weeks of age have adequate sweat volumes. Sweat testing should not be delayed in infants with a positive CF NBS test.