title: Salivary cortisol and cortisone by LC-MS/MS: validation, reference intervals and diagnostic accuracy in Cushing's syndrome.
abstract: BACKGROUND
  The Endocrine Society recommends late-night salivary cortisol (LNS-F) as a first-line screening test for Cushing's syndrome (CS). In the parotid gland, 11β-hydroxysteroid dehydrogenase type 2 inactivates cortisol (F) to cortisone (E), a known source of interference in the more frequently used immunoassays. A highly specific method is mandatory in determining salivary F and E: it is widely accepted that liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the best available technique for this purpose.
  
  
  METHODS
  A LC-MS/MS method with SPE of saliva samples was developed and validated. Appropriate awakening and bedtime reference ranges were established. The diagnostic performance for F, E and the ratio at bedtime was evaluated in 25 cases of CS.
  
  
  RESULTS
  The method was linear, with up to 55.4 nmol/L and 51.0 nmol/L, LLOQ of 0.51 nmol/L and 0.55 nmol/L, for F and E, respectively. Within-run and between-run imprecisions were <10% for both analytes. No ion suppression was observed. A cut-off of 2.4 nmol/L for LNS-F yielded a sensitivity of 100% and a specificity of 98% in the diagnosis of CS.
  
  
  CONCLUSIONS
  The analytical performance of this method justifies its introduction into clinical practice, thus allowing clinicians the opportunity to further investigate CS and other endocrine diseases.
authors.affiliation: U.O.C. of Laboratory Medicine, Department of Medicine, University of Padova, Padova, Italy. Electronic address: giorgia.antonelli@unipd.it.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Antonelli
authors.affiliation: U.O. of Endocrinology, Department of Medicine, University of Padova, Padova, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Ceccato
authors.affiliation: Department of Laboratory Medicine, University-Hospital of Padova, Padova, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Artusi
authors.affiliation: Department of Laboratory Medicine, University-Hospital of Padova, Padova, Italy.
authors.forename: Mariela
authors.initials: M
authors.lastname: Marinova
authors.affiliation: U.O.C. of Laboratory Medicine, Department of Medicine, University of Padova, Padova, Italy; Department of Laboratory Medicine, University-Hospital of Padova, Padova, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Plebani
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002851:Chromatography, High Pressure Liquid / Q000592:standards; D003348:Cortisone / Q000032:analysis*; D003480:Cushing Syndrome / Q000175:diagnosis* / Q000378:metabolism*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012463:Saliva / Q000737:chemistry*; D053719:Tandem Mass Spectrometry / Q000592:standards; D055815:Young Adult
chemical_list: D003348:Cortisone; D006854:Hydrocortisone
keywords: Cortisol; Cortisone; Cushing's syndrome; LC–MS/MS; Reference intervals; Saliva