LAUSR

Abstract Correlation between midnight and post dexamethasone salivary cortisone and cortisol and post dexamethasone serum cortisol concentrations in patients with unilateral and bilateral adrenal incidentalomas Background: The commonest functional abnormality in adrenal incidentalomas (AI) is autonomous cortisol secretion. Most guidelines recommend a 1 mg overnight dexamethasone suppression test (ONDST) as a screening test for this abnormality. This requires either a short stay or attendance to hospital as well as the inconvenience of venepuncture. Aim: To investigate the utility of using salivary samples in an ONDST by correlating post dexamethasone salivary cortisol (SaC) and cortisone (SaCn) and midnight salivary cortisol (MSaC) and cortisone (MSaCn) concentrations with post dexamethasone cortisol (SC). Methods: Using linear regression analysis we correlated post SC with SaC and SaCn and with MSaC and MSaCn. Results: We examined the results of 57 patients with unilateral or bilateral adrenal incidentalomas who underwent a 1 mg dexamethasone suppression test on our unit. The SC range <22 to 780, median 39 nmol/L, SaC <0.3 to 1.3, median 0.3 nmol/L, SaCn range 0.7 to 30.4, median 2.15 nmol/L, MSaC range <0.8 to 10.6, median 1.4 nmol/L and MSaCn range 2.3 to 44.9, median 8.25 nmol/L. There was a strong correlation between SaCn and SC (P<0.001; R squared 0.93) and a slightly weaker correlation of SaC (P=0.002, R squared 0.16) with SC. Both MSaCn and MSaCn correlated weakly with SC (P=0.004, R squared 0.15, for SaC and P=0.180, R squared 0.02 for SaCn) Conclusion: SC correlates best with SaCn followed by SaC followed by MSaCn and lastly MSaC. There is the potential for SaCn to be used instead of serum cortisol in the 1 mg ONDST. This would negate the need for venepuncture or the attendance to hospital for the test and could be more convenient for patients undergoing this test.