Introduction: Newborn premature infants are susceptible to develop relative adrenal insufficiency (AI) following transition from fetal to extrauterine life. Clinical signs of AI include hypoglycemia, dysbalanced electrolytes, fatigue and low blood pressure. Collecting serum cortisol samples itself is stressful for the infant, which challenges - in addition to analytic problems due to interference between fetal, placental and maternal derived steroids the interpretation of results. Saliva samples can be taken stressless and free cortisol can be measured excluding any analytical interference. However, the best diagnostic test for adrenal insufficiency in neonates has yet to be developed
Methods/Objective: The aim of this study was (1) to assess the feasibility of obtaining sufficient saliva samples from preterm newborns to allow measurement of free cortisol by enzyme immunoassay and (2) to assess the correlation, if any, between salivary free cortisol and serum cortisol in preterm infants between 32+0 and 36+6 weeks' gestational age at birth, who showed clinical signs for adrenal insufficiency. Patients with diagnosed congenital adrenals hyperplasia were excluded.
Results: Samples for 118 paired serum cortisol and saliva free cortisol levels from 43 preterm infants were analyzed. (1) 93.5% of samples collected had sufficient salivary volumes for measurement. (2) Despite being statistically significant (P<0.0001), the correlation (Spearman r=0.685) between serum and salivary cortisol was not strong.
Discussion: Salivary free cortisol measurement is feasible but cannot be used to accurately reflect serum total cortisol. Further studies comparing salivary free cortisol to serum cortisol and establishing normative data for saliva derived free cortisol levels in preterm newborns are needed before salivary cortisol can be used for diagnostic routine purposes. Finding the diagnosis of preterm AI remains challenging
19 - 21 Sep 2019
European Society for Paediatric Endocrinology