Interference Of Exogenous Glucocorticoids To Cortisol Measurement By Electro Chemiluminescence Immunoassay

Background and ObjectiveGlucocorticoid is an important endocrine hormone secreted by the adrenal cortex. It not only has an important physiological role, but also was widely used in clinical medicine as a frequently used drug. Cortisol or hydrocortisone is the most important human glucocorticoid. Cortisol, as an important glucocorticoid, can regulate the functions of cardiovascular system and immunologic system, and maintain metabolic homeostasis. Cortisol is also a part of the feedback mechanism in the immune system that turns excessive activity of immune system(inflammation) down. They are therefore used as a medicine to treat diseases caused by an overactive of immune system, and also used in inhibition of stress and in hormone supplement or substitute.The synthesis and secretion of cortisol are regulated by the hypothalamus-pituitary-adrenal axis. Cortisol measurement is of importance for evaluation the function of the hypothalamus-pituitary-adrenal axis, Therefore, whether the detection method can accurately reflect the function of endogenous hormone synthesis is especially important. Electro chemiluminescence immunoassay is the most advanced test technology, which is widely used in cortisol measurement.Synthetic glucocorticoids (exogenous glucocorticoids) are frequently used in clinic. The Structure and function of various synthetic glucocorticoids are very similar with the endogenous cortisol. So the exogenous glucocorticoids may interfere with the measurement of endogenous cortisol by electro chemiluminescence immunoassay.In this study, we use cortisone, prednisone, prednisolone, methylprednisolone, dexamethasone and betamethasone, six kinds of commonly used exogenous glucocorticoids as disruptors, and the test the serum cortisol under the influence of these disruptors, then take a screening and make an analysis of dose-relation about disruptors.Methods1Solution preparationTook each kinds of exogenous glucocorticoids, included cortisone, prednisone, prednisolone, methylprednisolone, dexamethasone and betamethasone dissolved into absolute ethyl alcohol respectively, forming six types of disruptor solution, the concentration of which is500mg/L.2Screening of disruptorsAdded10μL6kinds of disruptors solution above-mentioned into500μL serum respectively, forming six types of serum solution with different disruptors, the concentration of which is10mg/l, then took these six types of solution as the experimental groups. The control serum was added with10μL absolute alcohol. And then made a cortisol concentration measurement for the samples by automated electro-chemiluminescence immunoassay analyzer, and recorded the results.3Dose-relation analysisMixed the remaining serum samples, forming one sample. Diluted every type of disruptors solution above-mentioned into different concentrations, and added every diluted disruptor solution into mixed serum respectively, forming6kinds of serum disruptors solution with concentrations of0,0.05(5),0.1(10),0.2(20),0.5(50),1.0(100),2.0(200) and5.0(500)mg/L(μg/dL). After that, made a cortisol concentration measurement for these samples by automated electro chemiluminescence immunoassay analyzer respectively and repeatedly.4Statistical analysisSPSS17.0software was used for analysis of variance, paired T test and analysis of simple regression, the test level was a=0.05.Results1Screening of disruptorsThe cortisol level of the four experimental groups containing cortisone, prednisone, prednisolone and methylprednisolone respectively were higher than the upper limit of the detection, that is more than60μg/dL, It is clear that the tested level is extremly higher than the control group. The cortisol level of the two experimental group about dexamethasone and betamethasone were higher than that of the control group and the result of paired T test showed the difference was of statistically significance(group of dexamethasone:P=0.001, group of betamethasone:P=0.006).2Dose-relation analysisResults analysed by simple regression showed the relationship between the dose of six kinds of disruptors and the effect of interference. All six types of disruptors could interfere cortisol detection, and the cortisol detection value increased as increasing the dose of disruptors. However low-dose of disruptors (prednisone: c≦20μg/dL, methylprednisolone:c≦10μ/dL, dexamethasone:c≦200μg/dL, betamethasone:c≦50μg/dL) could have a negative interference on cortisol test, making the detection value less than the true value.The relative formula between cortisol detection and the dose of cortisone, prednisone, prednisolone, methylprednisolone, dexamethasone, and betamethasone were y=21.416+0.098x, y=17.056+0.018x, y=19.731+0.425x, y=19.086+0.52x, y=16.978+0.08x, y=17.104+0.551nx.ConclusionMeasurement of cortisol by electro chemiluminescence immunoassay can be interfered by six kinds of exogenous glucocorticoids include prednisone, prednisolone, methylprednisolone, dexamethasone, and betamethasone. And the interference is different by different exogenous glucocorticoids.Small doses of disruptors can produce a negative interference on cortisol detection, With the increasing of disruptors dose, negative effect of interference reduced, yet the positive effect of that increased.