15 Normal values and failure rate of sweat conductivity using Nanoduct Sweat Analysis System in healthy infants aged 4 days and 4 weeks

Abstract

Objective Nanoduct is a sweat analysis system to measure sweat conductivity. This test system needs only 3 microliter sweat (instead of >15 ul using the Macroduct collection method to determine chloride) which makes it especially applicable for infants, and results are available within 30 minutes. Methods From June 2013 to December 2014 Nanoduct (Wescor, Utah, USA) was tested in 261 healthy term infants at age 3–5 days (test 1) and 3–4 weeks (test 2). Results Mean age (sd) of the infants was 4.0 (1.5) days at test 1 and 27.0 (5.1) days at test 2; mean weight was 3.3 (0.36) kg and 4.2 (0.50) kg respectively. Mean (sd) test duration was 28 (6) and 26 (6) minutes respectively. Test 1 was successful in 159/261 (61%). Success of test 1 increased with weight, from 53% in the lowest quartile to 71% in the highest quartile (p = 0.02). There was no sweat in 79 and insufficient sweat production in 23 infants. Mean conductivity was 53.2 mmol/L (sd 15.5; range 17–114). Test 2 was successful in 226/240 infants (94%), with no sweat in 9 and insufficient sweat production in 5 infants. Success of test 2 was not significantly associated with weight (p = 0.12). Mean conductivity at date 2 was 35.7 mmol/l (sd 8.5; range 17–64). Conclusion The mean conductivity (95% and 99% confidence intervals) of sweat using the Nanoduct was 53 mmol/L (23–84; 13–93) on day 3–5 and 36 mmol/L (19–52; 11–62) at the age of 3–4 weeks. The failure rate of Nanoduct sweat test system was 39% on day 3–5 compared to 6% at the age of 3–4 weeks.