Predictors for the quantity not sufficient sweat collection for ionic
conductivity in newborns and young infants
Abstract
Background: Sweat conductivity (SC) is a semi-automated method widely
used as a screening test for Cystic Fibrosis. Quantity not sufficient
(QNS) is defined when collecting a volume lower than 15 μl of sweat
during 30 minutes. Objective: To verify the rate and factors related to
QNS for SC in newborns and young infants. Methods: Newborns and infants
aged less than three months that had undergone sweat conductivity after
two abnormal immunoreactive trypsinogen results, were recruited
prospectively and consecutively. Statistical analysis included
descriptive statistics, univariate and multivariate logistic regression.
Results: A total of 1020 individuals were included. Among them, the rate
of QNS was 8.9%. Subjects with gestational age <37 weeks
(OR=5.0), birth weight <2.000g (OR=3.5), and daily weight gain
<25g/day (OR=3.4) were more likely to produce an insufficient
quantity of sweat. Conclusion: Our results suggest that QNS rates for SC
could successfully fulfill the Cystic Fibrosis Foundation standards in
newborns and young infants. In cases of QNS, SC should be scheduled as
early as possible when the infant is older than 37 weeks (corrected
age).