title: Nanoduct sweat testing for rapid diagnosis in newborns, infants and children with cystic fibrosis.
abstract: Determination of chloride concentration in sweat is the current diagnostic gold standard for Cystic Fibrosis (CF). Nanoduct is a new analyzing system measuring conductivity which requires only 3 microliters of sweat and gives results within 30 minutes. The aim of the study was to evaluate the applicability of this system in a clinical setting of three children's hospitals and borderline results were compared with sweat chloride concentration. Over 3 years, 1,041 subjects were tested and in 946 diagnostic results were obtained. In 95 children, Nanoduct failed (9.1% failure rate), mainly due to failures in preterm babies and newborns. Assuming 59 mmol/L as an upper limit of normal conductivity, all our 46 CF patients were correctly diagnosed (sensitivity 100%, 95% CI: 93.1-100; negative predicted value 100% (95% CI: 99.6-100) and only 39 non CF's were false positive (39/900, 4.3%; specificity 95.7%, 95%CI: 94.2-96.9, positive predicted value 54.1% with a 95%CI: 43.4-65.0). Increasing the diagnostic limit to 80 mmol/L, the rate fell to 0.3% (3/900). CF patients had a median conductivity of 115 mmol/L; the non-CF a median of 37 mmol/L. In conclusion, the Nanoduct test is a reliable diagnostic tool for CF diagnosis: It has a failure rate comparable to other sweat tests and can be used as a simple bedside test for fast and reliable exclusion, diagnosis or suspicion of CF. In cases with borderline conductivity (60-80 mmol/L) other additional methods (determination of chloride and genotyping) are indicated.
authors: Department of Pediatrics, University of Berne, Berne, Switzerland.
authors: Marie-Claire
authors: MC
authors: Desax
authors: Roland A
authors: RA
authors: Ammann
authors: Jürg
authors: J
authors: Hammer
authors: Martin H
authors: MH
authors: Schoeni
authors: Jürg
authors: J
authors: Barben
mesh_terms: D002648:Child; D002675:Child, Preschool; D002712:Chlorides / Q000032:analysis; D019963:Clinical Chemistry Tests; D003550:Cystic Fibrosis / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D018709:Statistics, Nonparametric; D013542:Sweat / Q000737:chemistry*
chemical_list: D002712:Chlorides