The procedures used for collecting and assaying cortisol followed established protocols (for description, see5 (link)). Parents collected saliva samples from children twice per day (within 30 minutes of wake-up, and right before bedtime) over a 3-day period. Table 2 shows descriptive statistics of sampling times.
The saliva samples were stored in a freezer at −20°C prior to assay procedures. Samples were assayed using a high-sensitivity salivary cortisol enzyme immunoassay kit (Salimetrics, LLC, State College, Pennsylvania). All samples from a child were assayed in duplicate on the same plate to minimize variability. The intra-assay and interassay coefficients of variation fell below 3.7% and 6.4%, respectively.
The saliva samples were stored in a freezer at −20°C prior to assay procedures. Samples were assayed using a high-sensitivity salivary cortisol enzyme immunoassay kit (Salimetrics, LLC, State College, Pennsylvania). All samples from a child were assayed in duplicate on the same plate to minimize variability. The intra-assay and interassay coefficients of variation fell below 3.7% and 6.4%, respectively.
