Comparison of cortisol samples in the first two weeks of life in preterm infants

Background: Growing literature on negative childhood stress emphasizes the need to understand cortisol values from varying biomarker samples. Objective: This work aimed to examine cortisol samples for usability, associations, and individual stability in neonates. Subjects: The sample consisted of preterm infants (n=31). Materials and methods: Analyses on cortisol collected from cord blood and from saliva and urine samples on days 1, 7, and 14 included Spearman correlations and paired t-tests. Results: Usability rates were 80.6% (cord blood), 85.9% (saliva), and 93.5% (urine). Salivary and urinary cortisol levels had significant correlation on day 1 only (p=0.004). Significant differences in individual stability of cortisol concentrations existed except in urine on days 1 and 7 and in saliva on days 7 and 14. Conclusions: Usability was highest for urine samples. We found little correlation between cortisol sample levels at each time; individual stability of cortisol concentrations was minimal. Interpretation of cortisol findings in all studies should be performed cautiously.