Date of Defense:
Objectives: Neonatal Dried Blood Spots (DBS) are potentially very useful specimen in pediatric research because they represent a biochemical snapshot taken shortly after birth. The aim of our study was to develop Insulin-like growth factor-1 (IGF-1) and Cytokine (IL-8) assays on DBS. Previous studies examining regulators of fetal growth have demonstrated a positive correlation between cord blood serum levels of IGF-1 and infant birth weights. Studies have also shown a negative correlation between cord blood IL-8 levels and gestational age. We hypothesized that similar relationships will be seen with IGF-1, IL-8 levels measured in DBS obtained from infant heel sticks at birth and their weights and gestational ages at birth respectively.
Methods: We obtained neonatal DBS from various state newborn screening programs for our study. 114 test spots with associated birth weight, gestational age, sex, maternal age, race and state data were chosen at random within five birth weight, gestational age categories. IGF-1 and IL-8 levels were measured using a modified ELISA and Luminex assays respectively. Blood spot IGF-1 and IL-8 levels were correlated significantly with infant birth weights (r=0.27; p=0.008) and gestational ages (r=-0.34; p=0.02) respectively after adjusting for the mentioned demographic factors.
Results: Our results indicate that neonatal DBS obtained from heel sticks at birth may be employed as substitute specimen for serum samples to measure IGF-1 and IL-8 levels.
Conclusions: These bio-specimens are of great practical value especially in long-term cohort and retrospective studies examining prenatal/neonatal exposures and subsequent development of disease states.