Endocrine Abstracts

Background: Diagnosing endogenous Cushing’s syndrome (CS) is often challenging because of the difficulty in interpreting results of dynamic endocrine tests. One of the recommended initial tests is the measurement of late-night salivary cortisol (LNSaCl). Some articles describe added value of late-night salivary cortisone (LNSaCn) measurements. However, published cut-off values of LNSaCl and LNSaCn vary widely between studies, which may be related to different experimental set-ups.

Aim: The aim of this study was to establish the cut-off values for LNSaCl and LNSaCn that differentiate between patients with and without endogenous hypercortisolism using LC–MS/MS.

Methods: The study included data from consecutive patients who underwent dynamic endocrine function tests to evaluate endogenous hypercortisolism at Amsterdam UMC between December 2015 and February 2022. The indications for testing included clinical suspicion, adrenal or pituitary incidentalomas, or evaluation in the context of genetic diseases. Endogenous hypercortisolism was diagnosed or excluded based on follow-up of more than 12 months, histology, symptom reduction, and the need for hydrocortisone supplementation postoperatively. Salivary samples were collected between 2200 and 2359 h on two consecutive days and analyzed for cortisol and cortisone using an in-house developed and well standardized liquid chromatography coupled to mass spectrometry method (LC–MS/MS). Data analysis was based on the lowest of the two LNSaCl and LNSaCn measurements. The test’s diagnostic accuracy was evaluated using ROC curve analysis.

Results: Twenty-nine patients with endogenous CS (21 of pituitary and 8 of adrenal origin) and 497 patients without endogenous hypercortisolism were included. The median LNSaCl was 7.8 nmol/l (IQR: 8.5) for patients with CS (n=25 eligible measurements), and 1.0 nmol/l (IQR: 0.9) for patients without CS (P=<0.001, n=430 measurements). The median concentration of the LNSaCn measurements was 35.5 nmol/l (IQR: 30.8) for patients with CS (n=16 measurements), and 5.3 nmol/l (IQR: 4.5) for patients without CS (n=311 measurements, P=<0.001). For LNSaCl, a cut-off of 2.25 nmol/l provided the optimal diagnostic accuracy for endogenous hypercortisolism with a sensitivity of 96% and a specificity of 86% (positive predictive value (PPV)=28.6%, negative predictive value (NPV)=99.7%). For LNSaCn this was 15.5 nmol/l with a sensitivity of 93.8% and a specificity of 94.5% (PPV=46.9%, NPV=99.7%).

Conclusion: We established optimal cut-off values for cortisol and cortisone in saliva measured by LC–MS/MS. The cut-off of LNSaCn provided the highest accuracy. Using these cut-off values will add to the performance of screening for endogenous hypercortisolism and these can be used by other laboratories following method comparison.