title: The 10:00-11:00 pm urine cortisol/creatinine ratio. An alternative to late-night salivary cortisol for the diagnosis of Cushing's syndrome.
abstract: The aim of this study was to investigate interchangeability of two tests to diagnose Cushing's syndrome. We compared 10:00-11:00 PM urinary free cortisol/creatinine ratio (UFC/Cr) with late night 11:00 PM salivary cortisol (LNSC) in normal and obese controls vs. patients with Cushing's syndrome. Mean UFC/Cr did not differ between 69 normal and 62 obese controls (9.9 ± 7.9 vs. 9.7 ± 9.3) whereas 116 Cushing's patients had significantly higher values (277.0 ± 318.0; z: -11.1 and -10.2, respectively; p < 0.001). LNSC was 1.9 ± 1.2 nmol/l in 44 normal and 2.5 ± 1.6 in 45 obese subjects with no differences between them, but was significantly higher in 47 Cushing's patients (24.8 ± 23.3; z: -7.22 and -6.96, respectively, p < 0.001). Comparison of UFC/Cr and LNSC in samples obtained simultaneously showed that UFC/Cr was 12.0 ± 8.7 ng cortisol/mg creatinine in 34 normal, 12.3 ± 8.9 in 40 obese and 319.5 ± 333.4 in 35 CS subjects (p < 0.001 vs. normal and obese), whereas LNSC was 1.8 ± 1.2 nmol/l in normal, 2.6 ± 1.7 in obese and 24.6 ± 17.4 in CS patients (p < 0.001 vs. normal and obese); ROC curves showed comparable high sensitivity and specificity figures for the diagnosis of CS. We concluded that UFC/Cr test is easy to perform, readily available in routine laboratories, has high sensitivity and specificity, and offers a valuable alternative to LNSC in the study of Cushing's syndrome.
authors.affiliation: Fundación de Endocrinología (FUNDAENDO) y División Endocrinología, Hospital de Clínicas, Universidad de Buenos Aires, Argentina. E-mail: bodomingo@intramed.net.
authors.forename: Oscar D
authors.initials: OD
authors.lastname: Bruno
authors.forename: María A
authors.initials: MA
authors.lastname: Rossi
authors.forename: Lea
authors.initials: L
authors.lastname: Juárez-Allen
authors.forename: Héctor A
authors.initials: HA
authors.lastname: Serra
authors.forename: María C
authors.initials: MC
authors.lastname: Albiero
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002940:Circadian Rhythm; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D003480:Cushing Syndrome / Q000175:diagnosis* / Q000652:urine*; D003940:Diagnostic Techniques, Endocrine / Q000592:standards; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism / Q000652:urine*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000652:urine; D012372:ROC Curve; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013997:Time Factors; D055815:Young Adult
chemical_list: D003404:Creatinine; D006854:Hydrocortisone
keywords: Cushing's syndrome; salivary cortisol; urinary cortisol