An automated chemiluminescence immunoassay for the determination of cortisol and its application on Adrenal Vein Sampling

Introduction: Abnormal cortisol levels due to hypothalamic, pituitary or adrenal malfunction, such as in Cushing's syndrome and Addison's disease, can lead to severe metabolic imbalance. Current guidelines for the diagnosis of hypercortisolism recommend the measurement of cortisol in blood following stimulation or suppression tests, but also the measurement of integrated 24 hours cortisol secretion in urine or late night salivary cortisol. More recently, measurement of cortisol has also been proposed as a marker of selectivity of cannulation of the adrenal veins during adrenal vein sampling procedures. The latter, however, requires the availability of a very rapid cortisol measurement procedure.

Methods: We present here a competitive immunoassay for the rapid measurement of cortisol on a chemiluminescence analyzer (IDS-iSYS) in various matrices (serum, plasma, urine and saliva). To prove its suitability for rapid cortisol measurement, EDTA Plasma samples of adrenal vein sampling (AVS) procedures were analyzed for cortisol concentrations and compared to our routine method (Liaison, Diasorin).

Results: Using the new method, we found in AVS samples (n = 127) a good correlation to our routine method (y = 0.96x + 0.70, R²= 0.89). These results were available already after 8 min while for our routine method it takes 26 min.

Conclusion: The fully automated IDS-iSYS cortisol assay potentially presents a new, accurate and reliable immunoassay for all commonly used sample types on one platform. The extremely short time to first result makes the assay suitable also for use during diagnostic procedures like adrenal vein sampling.