Avtomatizirovannyy elektrokhemilyuminestsentnyy metod opredeleniya kortizola v slyune dlya diagnostiki endogennogo giperkortitsizma sredi patsientov s ozhireniem

Nighttime salivary cortisol (NSC) has been suggested to be a useful diagnostic test for Cushings syndrome (CS). However, the reference range and cut-off value are assay-specific and discordant. The goal of this study was to assess the analytical performance of automated elecrochemiluminiscence immunoassay method (ECLIA) in CS. Ninety eight healthy volunteers and 123 obese patients including 45 proved to be CS provided salivary samples collected by them at 23:00 using Sallivette. Two hundred and five subjects collected salivary samples for two consecutive days and samples from 197 subjects were frozen to perform Enzyme-linked immunosorbent assay (ELISA). Obese patients underwent the 1-mg overnight dexamethasone suppression test (1-DST). CS was confirmed by the histologic diagnosis after surgical treatment or autopsy. The reference range for healthy volunteer has been set 0,5-9,4 nmol/l. Reproducibility was assessed in all subjects by a day-to-day variability and reflected by an intraclass correlation coefficient of 0,785. The cut-off value of 9,4 nmol/l has been suggested to differentiate CS among obese patients to achieve sensitivity of 84,4% (95%confidence interval 71,2-92,2%); specificity of 92,3% (95%CI 84,2-96,4%) and diagnostic odds ratio 65,1 (95% CI 20,4-207,6). Likelihood ratio positive was 11,0 (95% CI 5,0-23,9), with a likelihood ratio negative of 0,17 (95%CI 0,08-0,33). The comparison of the total areas under the ROC-curve for the measurement of NSC once, twice with mean level by ECLIA, the same samples by ELISA and 1-DST have not shown any statistically significant difference among the tests performance. Conclusion: Based on its remarkable reproducibility, easy noninvasive nature, automated assay and at least similar diagnostic performance, NSC measured by ECLIA on Cobas e601 is a preferable first-line screening test for CS.

Cushing's syndrome, nighttime salivary cortisol, elecrochemiluminiscence immunoassay method, diagnostic test, obesity

1. Boscaro M., Arnaldi G. Approach to the patient with possible Cushing's syndrome // J. Clin. Endocrinol. Metab. - 2009. - Vol. 94. - Р. 3121-3131.

2. Nieman L.K., Biller B.M.K., Finding J.W., Newell-Price J., Savage M.O., Stewart P.M., Montori V.M. The diagnosis of Cushing's syndrome: an endocrine society clinical practice guideline // J. Clinical Endocrinology and Metabolism. - 2008. - Vol. 93. - Р. 1526-1540.

3. Mericq M.V., Cutler Jr.G.B. High fluid intake increases urine free cortisol excretion in normal subjects // J. Clin Endocrinol Metabolism. - 1998. - Vol. 83. - Р. 682-684.

4. Fenske M. How much "urinary free cortisol" is really cortisol during water dieresis in healthy individuals? // Clin Chem. - 2004. - Vol. 50. - Р. 1102-1104.

5. Dunn J.F., Nisula B.C., Rodbard D. Transport of steroid hormones: binding of 21 endogenous steroids to both testosterone-binding globulin in human plasma // J. Clin Endocrinol Metab. - 1981. - Vol. 53. - Р. 58-68.

6. Brien T.G. Human corticosteroid binding globulin // J. Clin Endocrinol (Oxf). - 1981. - Vol. 14. - Р. 193-212.

7. Read G.F., Walker R.F., Wilson D.W., Griffiths K. Steroid analysis in saliva for the assessment of endocrine function // Ann NY Acad of Sci. - 1990. - Vol. 95. - Р. 260-274.

8. Chen Y.M., Cintron N.M., Whitson P.A. Long-term storage of salivary cortisol samples at room temperature // Clin Chem. - 1992. - Vol. 38. - Р. 304.

9. Hiramatsu R. Direct assay of cortisol in human saliva by solid phase radioimmunoassay and its clinical applications // Clin Chim Acta. - 1981. - Vol. 117. - Р. 239-249.

10. Evans P.J., Peters J.R., Dyas J., Walker R.F., Riad-Fahmy D., Hall R. Salivary cortisol levels in true and apparent hypercortisolism // J. Clinical Endocrinology (Oxf). - 1984. - Vol. 20. - Р. 709-715.

11. Alexandraki K.I., Grossman A.B. Novel Insights in the diagnosis of Cushing's syndrome // J. Neuroendocrinology. - 2010. - Vol. 92, suppl.1. - Р. 35-43.

12. Restitute P., Galofre J.C., Gil M.J., Mugueta C., Santos S., Monreal J.I., Varo N. Advantage of salivary cortisol measurements in the diagnosis of glucocorticoid- related disorders // J. Clin Biochem. - 2008. - Vol. 41. - Р. 688-692.

13. Baid S.K., Sinaii N., Wade M., Rubino D., Nieman L.K. Radioimmunoassay and tandem mass spectrometry measurement of bedtime salivary cortisol levels: a comparison of assays to establish hypercortisolism // J. Clin Endocrinol. Metab. - 2007. - Vol. 92. - Р. 3102-3107.

14. Гончаров Н.П., Кация Г.В., Марова Е.И., Колесникова Г.С., Арапова С.Д., Рожинская Л.Я.: Использование ультрачувствительного метода опреде- ления биологически активного свободного кортизола в слюне для оценки глюкокортикоидной функции коры надпочеников // Проблемы эндокри- нологии. - 2008. - Т. 58. - № 3. - С. 27-35.

15. Raff H., Raff J.L., Finding J.W. Late-night salivary cortisol as a screening test for Cushing's syndrome // J. Clin Endocrinol Metab. - 1998. - Vol.83. - Р. 2681-2686.

16. Beko G., Varga I., Glaz E., Sereg M., Feldman K., Toth M., Racz K., Patocs A. Cutoff values of midnight salivary cortisol for the diagnosis of overt hypercortisolism are highly influenced by methods // Clin Chim Acta. - 2010. - Vol. 411. - Р. 364-367.

17. Carrozza C., Corsello S.M., Paragliola R.M., Palumbo F.I.S., Locantore P., Sferrazza A., Pontecorvi A., Zuppi C. Clinical accuracy of midnight salivary cortisol measured by automated electrochemiluminescence immunoassay method in Cushing's syndrome // Annals of Clinical Biochemistry. - 2010. - Vol. 47,pp. 228-232.

18. Vogeser M., Durner J., Seliger E., Auernhammer C. Measurement of latenight salivary cortisol with an automated immunoassay system // Clin Chem Lan Med. - 2006. - Vol. 44. - Р. 1441-1445.

19. Schindhelm R.K., Leur J.J., Rondeel J.M. Salivary cortisol as an alternative for serum cortisol in the low-dose adrenocorticotropic hormone stimulation test? // J. Endocrinol Invest. - 2010. - Vol. 33. - Р. 92-95.

20. Carroll T., Raff H., Finding J.W. Late-night salivary cortisol for the diagnosis of Cishing syndrome: a meta-analysis // Endocr.Pract. - 2009. - Vol. 15. - Р. 335-342.

21. Baid S.M., Rubino D., Sinaii N., Ramsey S., Frank A., Nieman L.K. Specificity of screening tests for Cushing's syndrome in an overweight and obese population // J. Clin Endocrinol Metab. - 2009. - Vol. 94. - Р. 3857-3864.