Improved Hypercortisolism and Hypocortisolism Screening with Automated Immunoassay
New Thresholds for Diagnosis
Research was presented at the 2011 Endocrine Society Annual Meeting on using salivary cortisol for diagnosing hypercortisolism and hypocortisolism. The study was done to establish reference ranges for an automated electrochemiluminescence immunoassay (ECLIA).
The study, done by researchers from Germany, was called “Salivary Cortisol as a Diagnostic Tool for Hyper- and Hypocortisolism: Improved Screening by an Automated Immunoassay.”
In this study, there were 40 patients with confirmed hypercortisolism. There were 12 who had Cushing’s disease, 2 with ectopic Cushing’s syndrome, and 26 with adrenal Cushing syndrome. These patients were compared to 115 healthy subjects and 45 control patients with adrenal masses (18 had non-functioning adenoma, 15 had pheochromocytoma, and 12 had aldosterone-producing adenoma).
Also, 63 patients with proven hypothalamic-pituitary disease were in the study; there were 54 with sellar masses and 9 with hormonal impairment.
Saliva sampling was performed at 11pm and 8am following low-dose dexamethasone suppression. The researchers used receiver operating characteristics (ROC) analysis to calculate the thresholds (with at least 95% sensitivity) for hypercortisolism. To define adrenal insufficiency, a peak serum cortisol level below 500 nmol/l during an insulin hypoglycemia test was used.
The researchers collected unstimulated saliva samples at 8am; ROC analysis was done to establish the lower and upper cutoffs with at least 95% specificity (for either adrenal insufficiency or adrenal sufficiency). A commercially-available ECLIA was used to perform the salivary cortisol measurements.
The study found that an 11pm salivary cortisol cutoff of 6.06 nmol/l (sensitivity 95%; specificity 92%; AUC 0.97) and a dexamethasone-suppressed salivary cortisol cutoff of 2.02 nmol/l (sensitibity 97%; specificity 86%; AUC 0.98) were calculated for diagnosing hypercortisolism.
In regards to the HPA axis, there was a lower cutoff of 3.21 nmol/l and an upper cutoff of 20.4 nmol/l that identified 12 out of 31 patients (39%) as having adrenal insufficiency; the same cutoffs identified 2 out of 32 patients (6%) as adrenal sufficient.
These newly-established thresholds give the practitioner an excellent tool for identifying both hypercortisolism and hypocortisolism by using an automated immunoassay. This will allow for a broader use of salivary cortisol as a routine diagnostic tool for hypercortisolism and hypocortisolism.