title: Screening for subclinical Cushing's syndrome in type 2 diabetes mellitus: low false-positive rates with nocturnal salivary cortisol.
abstract: The diagnosis of subclinical Cushing's syndrome (SCS) is important, but its relative rarity amongst patients with common metabolic disorders requires a simple test with a low false-positive rate. Using nocturnal salivary cortisol (NSC), which we first validated in patients with suspected and proven Cushing's syndrome, we screened 106 overweight patients with type 2 diabetes mellitus, a group at high risk of SCS and nontumoral hypothalamic-pituitary-adrenal axis perturbations. Our hypothesis was that a lower false-positive rate with NSC was likely, compared with that reported with the dexamethasone suppression test (DST) (10-20%), currently the foundation of diagnosis of SCS. No participant had clinically apparent Cushing's syndrome. Three participants had an elevated NSC but further testing excluded SCS. In this study, NSC had a lower false-positive rate (3%) than previously reported for the DST. Given the reported excellent performance of NSC in detection of hypercortisolism, the low false-positive rate in SCS suggests NSC may be superior to the DST for SCS screening. The NSC and DST should be compared directly in metabolic disorder patients; although our data suggest the patient group will need to be substantially larger to definitively determine the optimal screening test.
authors.affiliation: School of Medicine, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Gagliardi
authors.forename: I M
authors.initials: IM
authors.lastname: Chapman
authors.forename: P
authors.initials: P
authors.lastname: O'Loughlin
authors.forename: D J
authors.initials: DJ
authors.lastname: Torpy
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000368:Aged; D003480:Cushing Syndrome / Q000097:blood / Q000150:complications* / Q000175:diagnosis*; D003624:Darkness; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D006854:Hydrocortisone; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D012463:Saliva / Q000737:chemistry*
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone