The modification of technique of detection of free cortizol in urine.

Abstract

The detection of free cortizol in day urine is an informative marker for diagnosing conditions of hypo- and hypercorticism. Up to 1% of cortizol, in invariable form and with no association with proteins and secreted by adrenal cortex, is excreted with urine during a day. The level of free cortizol in urine has no dependencies from day variation of hormone in blood and hence it reflects total secretion of cortizol by adrenal cortex. Besides, as a rule a direct proportional dependence exists between level of free cortizol in urine and level of biologically active cortizol in blood. The developers of automated systems propose various techniques of detecting cortizol not only in blood but in other biological fluids too. In our laboratory techniques of detection of level of free cortizol in day urine were approved, modified and adapted meant for analyzer Vitros ECi (Ortho Clinical Diagnostics, Great Britain) and analyzer Cobas 6000 (Hoffmann-La Roche, Switzerland). The comparison of results obtained by these techniques was carried out (r = 0,96-1). The reproducibility of detection of cortizol was evaluated by force of analysis of every sample of urine in one and various settings. The spread made up to 1,7-3,7% for one setting and 5,2-6,7% for various settings. The schemes were proposed to detect level of free cortizol in urine for analyzer Vitros ECi (with preliminary extraction by diethyl ether and subsequent removal of water fraction by force of freezing), and also for analyzer Elecsys (with preliminary extraction by dichlormethane and subsequent separation of phases by centrifugation and evaporation of organic phase by force of vacuum concentrator).