Utility of midnight salivary cortisol measurement in the diagnosis of overt and subclinical Cushing's syndrome
Márta Sereg1, Judit Toke1, Attila Patócs2, Péter Igaz1, Nikolett Szucs1, Ibolya Varga2, Ágnes Szappanos1, Edit Gláz1, Károly Rácz1 & Miklós Tóth1
Background: Midnight salivary cortisol (SalC2400) measurement has been recently suggested as one of the first-line screening tests for hypercortisolism.
Aims: In our present study, we evaluated the clinical utility of the salivary cortisol (SalC) measurement in the diagnosis of both overt and subclinical Cushings syndrome.
Patients and methods: Patients with overt Cushings syndrome (n=23, group A) and those with subclinical Cushings syndrome due to incidentally discovered adrenal adenomas (n=18, group B) were sampled for serum cortisol (SerC) and SalC at 2400 and 0800 h. Urinary cortisol excretion (UFC) was measured and overnight low dose dexamethasone test (LDDST, 1 mg) was performed. The control group consisted of patients with the final diagnosis of inactive adrenocortical adenomas (n=40, group C) and of patients investigated for various reasons (severe obesity, hypertension, etc.) finally proved to be non-hypercortisolemic (n=70, group D). Receiver operating characteristics (ROC) analysis was performed to determine optimal cut-offs for diagnosis of both overt and subclinical hypercortisolism. Diagnostic power of each test was expressed as area under the curve (AUC) obtained by ROC analysis.
Results: Cortisol concentrations in each test except SerC0800 were higher in group A than in group B. The AUCs for discrimination of patients with overt or subclinical Cushings syndrome (n=41, groups A+B) from controls (n=110, groups C+D) in decreasing order were: LDDST 0.930, SeC2400 0.924, SalC2400 0.907, UFC 0.828, SalC0800 0.645 and SerC0800 0.642. SalC and UFC concentrations significantly correlated with body mass index in group D but not in the other groups.
Conclusion: The diagnostic utility of SalC2400 for the diagnosis Cushings syndrome was similar to LDDST and SerC2400. The differences in SalC2400 between overt and subclinical Cushings syndrome as well as the significant correlations between SalC/UFC and body mass index indicate that the diagnostic utility of SalC2400 is highly dependent on the composition of patient and control groups.