Clinical accuracy of midnight salivary cortisol measured by automated electrochemiluminescence immunoassay method in Cushing's syndrome.
BACKGROUND
The diagnosis of Cushing's syndrome (CS) represents a challenge for endocrinologists. Several screening tests are used, but none of them seems to be the gold standard for the diagnosis. The aim of this study was to confirm the diagnostic value of salivary cortisol (SC) as a first-level screening test and to evaluate the clinical performance of a electrochemiluminescence immunoassay (ECLIA) method.


METHODS
In 33 patients with a strong clinical suspicion of CS, we evaluated urinary free cortisol, circadian rhythm plasma cortisol (PC) and morning PC after low-dose dexamethasone suppression test (LDDST). At the same sampling times, we evaluated SC analysed by the same automated method. Correlation studies were evaluated by Spearman index (significance P < 0.05).


RESULTS
On the basis of biochemical results CS was confirmed in 21/33. SC was significantly correlated to PC at 12:00 and 23:00. Thus, we chose 8.3 nmol/L as midnight SC cut-off value with 100% sensitivity and 97.4% specificity. The cut-off chosen after LDDST was 1.7 nmol/L (100% sensitivity and 72% specificity).


CONCLUSIONS
SC assay showed a good clinical accuracy and the ECLIA method can be used in clinical routine to obtain fast results easily.
Carrozza
Cinzia
C
Institute of Biochemistry and Clinical Biochemistry, Catholic University School of Medicine, Rome, Italy. ccarrozza@ rm.unicatt.it
Corsello
Salvatore Maria
SM
Paragliola
Rosa Maria
RM
Ingraudo
Francesca
F
Palumbo
Sara
S
Locantore
Pietro
P
Sferrazza
Antonella
A
Pontecorvi
Alfredo
A
Zuppi
Cecilia
C
D000328:Adult; D003480:Cushing Syndrome / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*
D006854:Hydrocortisone