Specificity of screening tests for Cushing's syndrome in an overweight and obese population.
BACKGROUND
Recent reports suggest a higher prevalence (1-5%) of Cushing's syndrome in certain patient populations with features of the disorder (e.g., diabetes), but the prevalence in the overweight and obese population is not known.


OBJECTIVE
The aim of the study was to evaluate the diagnostic performance of screening tests for Cushing's syndrome in overweight and obese subjects with at least two other features of the disorder.


METHODS
We conducted a cross-sectional prospective study.


METHODS
A total of 369 subjects (73% female) completed two or three tests: a 24-h urine cortisol, and/or late-night salivary cortisol, and/or 1 mg dexamethasone suppression test (DST). If any result was abnormal [based on laboratory reference range or cortisol after DST > or = 1.8 microg/dl (50 nmol/liter)], tests were repeated and/or a dexamethasone-CRH test was performed. Subjects with abnormal DST results and a low dexamethasone level were asked to repeat the test with 2 mg of dexamethasone.


RESULTS
In addition to obesity, subjects had a mean of five to six features of Cushing's syndrome. None was found to have Cushing's syndrome. Test specificities to exclude Cushing's syndrome for subjects who completed three tests were: urine cortisol, 96% [95% confidence interval (CI), 93-98%]; DST, 90% (95% CI, 87-93%); salivary cortisol, 84% by RIA (95% CI, 79-89%) and 92% by liquid chromatography-tandem mass spectrometry (95% CI, 88-95%). The combined specificity (both tests normal) for all combinations of two tests was 84 to 90%, with overlapping CIs.


CONCLUSIONS
These data do not support widespread screening of overweight and obese subjects for Cushing's syndrome; test results for such patients may be falsely abnormal.
Baid
Smita K
SK
The Program in Reproductive and Adult Endocrinology, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1109, USA.
Rubino
Domenica
D
Sinaii
Ninet
N
Ramsey
Sheila
S
Frank
Arthur
A
Nieman
Lynnette K
LK
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone / Q000378:metabolism*; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism* / Q000652:urine; D008297:Male; D008403:Mass Screening / Q000379:methods / Q000592:standards; D008875:Middle Aged; D009765:Obesity / Q000150:complications; D050177:Overweight / Q000150:complications* / Q000175:diagnosis; D015995:Prevalence; D011446:Prospective Studies; D012463:Saliva / Q000378:metabolism*; D012680:Sensitivity and Specificity; D055815:Young Adult
D015415:Biomarkers; D003907:Dexamethasone; D006854:Hydrocortisone