Cutoff values of midnight salivary cortisol for the diagnosis of overt hypercortisolism are highly influenced by methods.
BACKGROUND
Midnight salivary cortisol (MSC) concentration has been considered as a sensitive marker of overt hypercortisolism. Because no studies on commercially available automated, non-isotopic MSC assays have been reported, we determined and compared the diagnostic performance of an automated electrochemiluminescent immunoassay (ECLIA, Elecsys E170) and an in-house radioimmunoassay (RIA) for MSC measurement.


METHODS
The study involved 126 consecutive patients referred for evaluation because of symptoms of Cushing's syndrome, obesity, or the presence of incidentally discovered adrenal adenoma. Using detailed clinical, hormonal and radiological evaluation overt endogenous hypercortisolism was confirmed in 9 patients and was excluded in 117 patients.


RESULTS
ROC analysis indicated that the best performance of MSC was obtained at cutoff value of 0.35 microg/dl using ECLIA (sensitivity, 100%; specificity, 88%) and 0.29 microg/dl (sensitivity, 100%; specificity, 71%) using RIA. When the findings were compared to those obtained from low dose dexamethasone test, both ECLIA and RIA of MSC showed a better diagnostic performance.


CONCLUSIONS
MSC measurement is useful for the diagnosis of overt hypercortisolism but the cutoff value is highly dependent on the method used. We recommend the use of automated ECLIA for MSC assay, and we propose further studies on other automated immunoassay analyzers potentially suitable for MSC measurements.
Beko
Gabriella
G
Central Isotope and Clinical Laboratory, Semmelweis University, Hungary.
Varga
Ibolya
I
Glaz
Edit
E
Sereg
Marta
M
Feldman
Karolina
K
Toth
Miklós
M
Racz
Karoly
K
Patocs
Attila
A
D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D018246:Adrenocortical Adenoma / Q000175:diagnosis*; D000328:Adult; D015415:Biomarkers / Q000097:blood; D003480:Cushing Syndrome / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D009765:Obesity / Q000175:diagnosis*; D012372:ROC Curve; D011863:Radioimmunoassay; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity
D015415:Biomarkers; D006854:Hydrocortisone