Nighttime salivary cortisol measurement as a simple, noninvasive, outpatient screening test for Cushing's syndrome in children and adolescents.

Abstract

There is currently no optimal test to screen for endogenous Cushing's syndrome (CS) in children. Traditional 24-hour urine or midnight serum cortisol values may be difficult to obtain or elevated by venipuncture stress. We hypothesized that salivary cortisol measurement is a reliable way to screen for CS in children. Sixty-seven children (5-17 years) were studied: 24 obese volunteers, 29 non-obese volunteers, and 14 children with CS. Saliva was obtained at 7:30 AM, bedtime, and midnight for measurement of free cortisol by radioimmunoassay. Salivary cortisol was detectable in all morning and evening samples from patients with CS but was frequently undetectable in healthy children at bedtime (66%) and at midnight (90%). With cut points that excluded healthy children, a midnight salivary cortisol value of 7.5 nmol/L (0.27 microg/dL) identified 13 of 14 patients with CS, whereas a bedtime value >27.6 nmol/L (1 microg/dL) detected CS in 5 of 6 patients. The diagnostic accuracies of midnight salivary cortisol and urinary free cortisol per square meter were the same (93%). Salivary cortisol measurement at bedtime or midnight rules out CS in nearly all cases. Nighttime salivary cortisol sampling is thus a simple, accurate way to screen for hypercortisolism in children.