The Turkish Journal of Pediatrics
2012 , Vol 54 , Num 6
Sweat Conductivity Test: Can It Replace Chloride Titration for Cystic Fibrosis Diagnosis?
Pediatric Pulmonology Unit, Department of Pediatrics, Hacettepe University Faculty of Medicine, Ankara, Turkey.
E-mail: guzincinel@yahoo.com
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.
Keywords :
cystic fibrosis, diagnosis, sweat conductivity, sweat chloride concentration.