Endocrine Abstracts

Introduction: Midnight salivary cortisol measurement (MSC) has been recently introduced as a diagnostic test for hypercortisolism. The aim of our study was to compare the diagnostic value of two methods of screening for Cushnig’s syndrome (CS): MSC and 24-h urinary free cortisol (UFC), wildely accepted as a ‘gold standard’ for this diagnosis.

Patients and methods: Three groups were studied: 30 patients with CS (mean age±S.D., 39.9±12.8 y, f/m 25/5, BMI 29.5±7.2 kg/m²), 34 with metabolic syndrome (MS) (41.1±13.6 y, f/m 24/10, 36.5±4.8 kg/m²) and 40 healthy normal weight controls (37.2±9.3 y, f/m 24/16, 23.4±2.8 kg/m²). Saliva was sampled at midnight (Salivette, Sarstedt^®). Urine was collected over 24 hours at the same day. An electrochemiluminescence immunoassay was used to measure salivary cortisol. UFC was assessed by a radioimmunoassay.

Results: Mean MSC in healthy volunteers, patients with MS and CS was 8.3±3.6, 8.1±4.5 and 33.1±21.7 nmol/l, respectively. Mean UFC was 129.1±72.7, 124.25±106.1 and 773.7±761.7 nmol/d. No significant difference was found between MSC and UFC in healthy controls and MS (P>0.05). By contrast, MSC and UFC were significantly higher in patients with CS (P<0.0001) as compared to both other groups. The cut-off point of 14.2 nmol/l for MSC yielded a sensitivity of 93.3% and a specificity of 94.2%. The cut-off point of 222 nmol/d for UFC showed a sensitivity of 100% and a specificity of 90%. Analysis of the areas under the curve (AUC) showed no significant difference between MSC and UFC (P<0.05, AUCMSC=0.984±0.01 (0.965–1.000); AUCUFC=0.975±0.01 (0.948–1.000) (mean±S.E.M. (confidentail interval of 95%)).

Conclusion: MSC and UFC determination have comparable diagnostic value. They both have reliably high sensitivity and specificity. We recommend the use of MSC as a first-line screening test for CS because of its convenience, escpecially in the ambulatory practice.