ESPE Abstracts

Introduction: The gold standard for the diagnosis of adrenal insufficiency (AI) is the ACTH stimulation test. According to the guidelines approved by the European Endocrine Society, the ACTH stimulation test should be performed with the administration of the standard dose of i.v. Synachten® 250 µg for adults and children aged ≥ 2 years (infants should receive 15 µg/kg, children ≤ 2 years 125 µg). In many clinical settings a Synachten® dose of 1 µg is currently used as an alternative to the standard dose ACTH stimulation test, because several studies have shown that both high dose ACTH test (HDT) and low dose ACTH test (LDT) have similar diagnostic accuracy. In last years, salivary cortisol has been proposed as an alternative to serum cortisol because it is less invasive and reflects free cortisol better than serum cortisol. We aimed to evaluate the reliability of salivary cortisol compared to serum cortisol for diagnosing AI in children that underwent HDT and LDT and to evaluate the sensitivity and specificity of salivary cortisol.

Methods: Data were collected retrospectively in the reference period 2015-2020. All patients were younger than 18 years of age. Salivary and serum cortisol values derived by 80 ACTH stimulation tests were obtained. For the HDT salivary and serum samples were collected at the baseline and after 30 and 60 minutes from ACTH i.v. administration, while for the LDT samples were collected at baseline and after 10, 20, 30, 40 and 60 minutes after the stimulation. A serum cortisol level >420 nmol/l ruled out AI.

Results: 24 HDT were obtained. The correlation coefficients between serum and salivary cortisol were 0.80 at t0, 0.48 at t30 and 0.75 at t60. All patients were adrenal sufficient. The number of LDT was 56: in 41% the peak of serum cortisol was indicative of insufficient adrenal function. The correlation coefficients between serum and salivary cortisol were 0.59 at t0 and 0.33 at the peak. For a cut-off of salivary cortisol <15 nmol/l, we calculated a sensitivity of 73.9% and a specificity of 69.6%.

Conclusions: Our data do not support salivary cortisol as a valid alternative to serum cortisol during LDT. In regard to the HDT, data about the correlation between salivary and serum cortisol are more encouraging but further studies are needed.