title: Clinical accuracy of midnight salivary cortisol measured by automated electrochemiluminescence immunoassay method in Cushing's syndrome.
abstract: 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.
authors.affiliation: Institute of Biochemistry and Clinical Biochemistry, Catholic University School of Medicine, Rome, Italy. ccarrozza@ rm.unicatt.it
authors.forename: Cinzia
authors.initials: C
authors.lastname: Carrozza
authors.forename: Salvatore Maria
authors.initials: SM
authors.lastname: Corsello
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Paragliola
authors.forename: Francesca
authors.initials: F
authors.lastname: Ingraudo
authors.forename: Sara
authors.initials: S
authors.lastname: Palumbo
authors.forename: Pietro
authors.initials: P
authors.lastname: Locantore
authors.forename: Antonella
authors.initials: A
authors.lastname: Sferrazza
authors.forename: Alfredo
authors.initials: A
authors.lastname: Pontecorvi
authors.forename: Cecilia
authors.initials: C
authors.lastname: Zuppi
mesh_terms: 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*
chemical_list: D006854:Hydrocortisone