Clinical Evaluation of the Troponin I Assay on Radiometer AQT90 FLEX and Beckman Coulter UniCel DxI 800 Analyzers

Background: High sensitive troponin assay methods used in emergency departments and those used in hospital laboratories are needed with low imprecision of the analytical method aligned along the cut-off. Methods: Presented is a method for adjusting the Troponin I (TnI) assay on the AQT90 FLEX analyzer (Radiometer) to the UniCel DxI 800 immunoassay system (Beckman Coulter) by correlation analysis using the Passing-Bablok method, followed by verification using receiver operating characteristic (ROC) analysis. This allows a uniform TnI cut-off to be applied to the use of different immunoassay systems in both the emergency department and in hospital laboratory settings. Finally, an imprecision profile of the TnI assay methods is applied to present a tool that allows for the discrimination of significant TnI results from imprecise measurements produced by the immunoassay system during repeated measurements. Results: For TnI, the equation of the best-fit lines with which all AQT90 FLEX results can be adapted to the UniCel DxI 800 is: UniCel DxI = 4.9524 AQT90 FLEX + 0.003. The imprecision of TnI can be calculated using the mathematical relationship described by Reed et al. from the assay's coefficient of variation and the difference between the first TnI result to the second TnI result. Conclusions: It is recommended to use a slope of 4.9524 and an intercept of 0.003 to adjust the TnI values of the AQT90 FLEX to the UniCel DxI 800 assay systems. Clinically relevant, i.e., significant TnI changes (rise or fall), can be reliably interpreted by accounting for the disparate results and the imprecision profile of the TnI assay method by applying the mathematical relationship described by Reed.