title: Sweat conductivity test: can it replace chloride titration for cystic fibrosis diagnosis?
abstract: Although sweat conductivity values are well matched with chloride concentrations for cystic fibrosis (CF) diagnosis, sweat conductivity is not accepted as a definitive diagnostic tool but only a screening method. The aim of this study was to compare the sweat chloride measurements and sweat conductivity values of our patients, and to determine cut-off values of conductivity for making or excluding a CF diagnosis. Fifty-nine CF patients, 10 patients with elevated sweat tests and 69 non-CF patients were included in the study. The mean conductivity values were 123 (64-157) mmol/L, 75.1 (60-93) mmol/L and 39 (18-83) mmol/L in the CF, elevated sweat test and control groups, respectively. The mean chloride concentration values were 107.5 (35-166) mEq/L, 48 (42-76) mEq/L and 25 (11-39) mEq/L in the CF, elevated sweat test and control groups, respectively. Spearman correlation test determined a strong correlation between conductivity and chloride concentration values (r=88%, p<0.001) in all subjects. According to the receiver operating characteristic (ROC) curve graph, the best conductivity cut-off value to make the CF diagnosis was found to be 90 mmol/L and to exclude the CF diagnosis was 70 mmol/L. We suggest that the conductivity measurement is as reliable as quantitative sweat chloride analysis to diagnose or exclude CF, and it can be used as a diagnostic test in addition to screening.
authors.affiliation: Pediatric Pulmonology Unit, Department of Pediatrics, Hacettepe University Faculty of Medicine, Ankara, Turkey. guzincinel@yahoo.com.
authors.forename: Güzin
authors.initials: G
authors.lastname: Cinel
authors.forename: Deniz
authors.initials: D
authors.lastname: Doğru
authors.forename: Ebru
authors.initials: E
authors.lastname: Yalçın
authors.forename: Uğur
authors.initials: U
authors.lastname: Özçelik
authors.forename: Nermin
authors.initials: N
authors.lastname: Gürcan
authors.forename: Nural
authors.initials: N
authors.lastname: Kiper
mesh_terms: D002648:Child; D002712:Chlorides / Q000032:analysis*; D003550:Cystic Fibrosis / Q000175:diagnosis*; D004553:Electric Conductivity; D005500:Follow-Up Studies; D006801:Humans; D012372:ROC Curve; D013542:Sweat / Q000737:chemistry* / Q000502:physiology*
chemical_list: D002712:Chlorides