SAT-355 Comparison of Two Serum Cortisol Immunoassays versus Liquid Chromatography: Tandem Mass Spectrometry (LC-MS/MS)

Accurate measurement of serum cortisol is required to diagnose and treat adrenal disorders. The most widely used methods in clinical laboratories for serum cortisol measurement are immunoassays which are offered in numerous commercial kits and on automated platforms. The LC-MS/MS is the gold-standard method to quantify serum steroids due its highest specificity, however it is a laborious methodology. Objective: to compare serum cortisol levels measured by two immunoassays versus LC-MS/MS. Methods: 35 routine serum samples (range: 1.1 to 50.0 ug/dL) were measured by Access Cortisol in Unicel DxI800 (Beckman Coulter), Architect Cortisol in i2000 Architect (Abbott) and LC-MS/MS in Xevo-TQ-S (Waters). Results were compared by Deming regression analysis and mean bias were used to describe the relationship between LC-MS/MS and Access and Abbott immunoassays, respectively. Results: Beckman and Abbott immunoassays showed similar cortisol concentrations (mean bias: 0.366%). Both immunoassays showed close agreement with LC-MS/MS results. Deming regression analysis showed a slope of 0.99 (0.85 to 1.134) an intercept of 1.334 (-1.345 to 4.014) in LC-MS/MS vs Beckman comparison; a slope of 1.008 (0.906 to 1.110) an intercept of 1.164 (-0.766 to 3.094) in LC-MS/MS vs Abbott comparison. The mean positive bias of Beckman and Abbott versus LC-MS/MS were 8.38% e 8.78%, respectively. Conclusion:Both Beckman and Abbott Cortisol immunoassays presented similar results in comparison of cortisol LC-MS/MS measurement, which evidence that these assays are suitable and reasonable methods for routine serum cortisol determination.