Circadian rhythm (CR) O, salivary cortisol (SAF) in children and adolescents using an ultrasensitive electrochemiluminescence immunoassay (ECLlA)

BALLERINI, MARÍA GABRIELA; AMARO, ANDREA; OTERO, PATRICIA; BERGADA IGNACIO; ROPELATO, MARÍA GABRIELA

Milan

Congreso; 9th Joint Meeting of Pediatric Endocrinology; 2013

ENDO, SLEP

Page 72 Abstr P1 d1 239 Background: Only one study described SAF CR in childhood using ECLIA. In adults, a cut-off decrease of cortisol at night (D%»50% was suggested for CR establishment. This evaluation is stilllacking for SAF in children. Objective: To evaluate CR of SAF in childhood using ECLIA. Methods: Prospective, transversal study of SAF in 63 steroid-free children (2-18 ys;28 girls). Samples were obtained in the moming (mSAF; median: 8:00AM) and at night (nSAF, ¡1:00PM) using plastic tubes. The collection procedure was evaluated by a questionnaire. SAF was directIy measured by ECLlA-Cortisol (Cobas-e411, Roche). Analytical performance of the SAF measurement was evaluated (CLSI evaluator protocols). SAF interindividual variation (iCV%) and the %D= [(mSAF-nSAF)/mSAF]xIOO were calculated. Influence of age, gender and BMI on SAF and %D was assessed. Serum cortisol concentration (F) vs SAF correlation was assessed in other 40 independent patients. Results: Total CVs< 15.3%, functional sensitivity=1.5 nmol/L, linearity (r=O.9945) and recoveries>80% were verified. SAF and F were significantly associated (r=O.75, p< 0.0001). 57/63 children referred no difficulties in salivary coJlection. mSAF and nSAF wideJy varied [mSAF iCV%: 49%, median;range (nmol/L): 16.1;2.9-36.7 and nSAF: 48%, 4.6;1.5-7.9, p< 0.0001). mSAF and nSAF did not vary with sex or BMI. nSAF (r= 0.54, p< 0.05) and %D (r= -0.58, p< 0.01) were associated with age. nSAF 97.5thcentile was 5.5 and 7.8 nmol/L for children < 10 years and >10 years, respectively (p=O.017). Interindividual D% variation was 22%. %D was >47% in children< lO years and >36% in >lOyears (p=O.004). Conclusion: Ultrasensitive SAF measurement cJearly demonstrated CR of cortisol without sex- or BMI-related changes. Our findings suggest that age should be taken into account when evaluating noctumallevels offree cortisol in saliva. Preliminarily results also suggest that a %D>36 in children < 10 years and >47% in older children may reflect CR indemnity. Poster