Salivary cortisol for assessment of hypothalamic-pituitary-adrenal (HPA) axis function in asthmatic children on inhaled corticosteroids (ICS)

Background/Aim: Sampling for salivary cortisol (SC) determination is a pain free procedure and thus useful in the pediatric age group. Our aim was to compare Low Dose ACTH (LDST) salivary test with the classical blood test as well as the diurnal variation in salivary cortisol concentration for the assessment of HPA axis activity of asthmatic children on ICS. Methods: LDST was performed in 62 asthmatic children (43 males, median age 7.9 yrs) before and after 3 months treatment with ICS. During the test, samples for SC were obtained simultaneously with serum samples (at 0-30-60 min). Patients sampled their own saliva between 09:00 and 21:00 hours (every three hours) for a whole day before and after treatment. Results: A significant positive correlation was found between salivary and serum cortisol levels at 0' 30' and 60' after ACTH administration (R:0.818, p<0.001). Circadian rhythm cortisol parameters: cortisol awakening response, mean level and range of diurnal changes, correlated with serum cortisol at 60'(R:0.308, p<0.025; R:0.316 p=0.022; R:0.318, p=0.026) and SC at 0' (R:0.398, p=0.003; R:0.401, p=0.002; R:0.356, p=0.01), 30' (R:0.402, p=0.002; R:0.385, p=0.003; R:0.404, p=0.003) and 60' (R:0.303, p=0.041; R:0.368, p=0.009). Conclusion: The salivary low dose ACTH test yields results that parallel the response of serum cortisol to ACTH and may provide an alternative to the blood test for HPA axis function evaluation. Diurnal SC variation may offer a dynamic evaluation over a day with none intervention.