title: Sweat conductivity and coulometric quantitative test in neonatal cystic fibrosis screening.
abstract: OBJECTIVE
  To compare the results obtained with the sweat test using the conductivity method and coulometric measurement of sweat chloride in newborns (NBs) with suspected cystic fibrosis (CF) in the neonatal screening program.
  
  
  METHODS
  The sweat test was performed simultaneously by both methods in children with and without CF. The cutoff values to confirm CF were >50 mmol/L in the conductivity and >60 mmol/L in the coulometric test.
  
  
  RESULTS
  There were 444 infants without CF (185 males, 234 females, and 24 unreported) submitted to the sweat test through conductivity and coulometric measurement simultaneously, obtaining median results of 32 mmol/L and 12 mmol/L, respectively. For 90 infants with CF, the median values of conductivity and coulometric measurement were 108 mmol/L and 97 mmol/L, respectively. The false positive rate for conductivity was 16.7%, and was higher than 50 mmol/L in all patients with CF, which gives this method a sensitivity of 100% (95% CI: 93.8-97.8), specificity of 96.2% (95% CI: 93.8-97.8), positive predictive value of 83.3% (95% CI: 74.4-91.1), negative predictive value of 100% (95% CI: 90.5-109.4), and 9.8% accuracy. The correlation between the methods was r=0.97 (p>0.001). The best suggested cutoff value was 69.0 mmol/L, with a kappa coefficient=0.89.
  
  
  CONCLUSIONS
  The conductivity test showed excellent correlation with the quantitative coulometric test, high sensitivity and specificity, and can be used in the diagnosis of CF in children detected through newborn screening.
authors.affiliation: Serviço de Referência em Triagem Neonatal (SRTN), Fundação Ecumênica de Proteção ao Excepcional (FEPE), Curitiba, PR, Brazil. Electronic address: mussetd@hotmail.com.
authors.forename: Mouseline Torquato
authors.initials: MT
authors.lastname: Domingos
authors.affiliation: Department of Pediatrics, Universidade Federal do Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Neiva Isabel Rodrigues
authors.initials: NI
authors.lastname: Magdalena
authors.affiliation: Department of Pediatrics, Universidade Federal do Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Mônica Nunes Lima
authors.initials: MN
authors.lastname: Cat
authors.affiliation: Serviço de Referência em Triagem Neonatal (SRTN), Fundação Ecumênica de Proteção ao Excepcional (FEPE), Curitiba, PR, Brazil.
authors.forename: Alexandra Mitiru
authors.initials: AM
authors.lastname: Watanabe
authors.affiliation: Department of Pediatrics, Universidade Federal do Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Nelson Augusto
authors.initials: NA
authors.lastname: Rosário Filho
mesh_terms: D002712:Chlorides / Q000032:analysis*; D003430:Cross-Sectional Studies; D003550:Cystic Fibrosis / Q000175:diagnosis*; D004553:Electric Conductivity; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015997:Neonatal Screening; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013542:Sweat / Q000737:chemistry*
chemical_list: D002712:Chlorides
keywords: Conductivity; Condutividade; Coulometric measurement; Cystic fibrosis; Dosagem coulométrica; Fibrose cística; Neonatal screening; Pilocarpina; Pilocarpine; Sweat test; Teste do suor; Triagem neonatal