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Rate and predictors of insufficient sweat volume in very young infants after pilocarpine gel iontophoresis: prospective, population-based study
  1. Paulo Camargos,
  2. Renata Marcos Bedran,
  3. Cristina Gonçalves Alvim,
  4. Olívia Gonçalves Sader
  1. Department of Pediatrics, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
  1. Correspondence to Professor Paulo Camargos, Pediatrics, Universidade Federal de Minas Gerais, Belo Horizonte 31130-100, Brazil; pcamargs{at}


Objective To verify the rate and predictors of ‘quantity not sufficient’ (QNS) among Brazilian infants younger than 3 months with positive newborn screening (NBS) for cystic fibrosis (CF).

Design Prospective, population-based study.

Setting Public Statewide Newborn Screening Programme where the incidence rate of CF is ≈1:11 000.

Patients Subjects with positive two-tiered immunoreactive trypsinogen.

Interventions Sweat induction and collection were performed in the same facility; one sweat sample was obtained per individual.

Main outcome measures The QNS rate and its predictors; analysis corresponded to the day of sweat collection.

Results Among the 975 participants, QNS rates for 10 and 15 µL were 3.6% (95% CI 2.5% to 4.9%) and 8.3% (95% CI 6.6% to 10.2%). Infants weighing >3056 and >3845 g and with gestational age higher than 37 weeks had a greater likelihood (5.5 and 6.7, and 2.7 and 5.8 times more, respectively) of avoiding QNS than their peers.

Conclusion QNS rates fulfilled the requirements, but predictors differed from those recommended by the Cystic Fibrosis Foundations guidelines.

  • Cystic Fibrosis
  • Global Health

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Contributors PC conceived the study and its design, had primary responsibility for protocol development, contributed to the investigation, methodology, project administration, validation and verified the underlying data; conception, writing, editing and revising of the manuscript. PC is the guarantor. RMB verified the underlying data, contributed to the conception, writing, revision and editing of the manuscript. CGA contributed to the manuscript’s conception, writing, editing and critical revision. OGS contributed to data collection, interpretation and analysis. All authors confirm that they had full access to all the data in the study and accept responsibility for submitting it for publication.

  • Funding This work was supported by the Brazilian Council for Research and Technological Development, grant number 486201/2013-9, to PC.

  • Disclaimer The funding body had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; and decision to submit the manuscript for publication.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.