Comparability of Beckman Coulter Cardiac Troponin I Assays.

Objective: Cardiac troponin I (cTnI) is one of the most sensitive and specific biomarkers of myocardial injury. The rise and/or fall of cardiac troponins above the 99th percentile of the upper reference limit (URL) is required in the assessment of acute myocardial infarction.

Methods: We analyzed the variation between the Beckman Coulter contemporary cTnI AccuTnI+3 assay and high sensitivity cTnI (hs-cTnI) assay tested on DXI 800 using 424 patient specimens with troponin levels ranging from 0-16754 ng/L. We also analyzed the concordance of the same assay hs-cTnI on different Beckman Coulter instruments Access 2 and DXI 800 using 115 patient specimens with troponin levels ranging from 2-100466 ng/L.

Results: The between-method comparison of AccuTnI+3 and hs-cTnI on DXI 800 showed a good correlation with the slope of 1.003, correlation coefficient (CC) of 0.9590, and bias of -40.65 (-5.16%). However, comparison of AccuTnI+3 and hs-cTnI in 103 patients with troponin less than 20 ng/L, the 99th percentile of the URL for male, showed the slope of 1.325, CC of 0.7462, and bias of 1.91 (21.53%). The within-method comparison of hs-cTnI on Access 2 and DXI 800 showed the slope was 1.130 with CC of 0.9915, and bias of 840.4 (10.6%). Further examination of the results revealed that hs-cTnI levels were more comparable at levels less than 200 ng/L, with a slope of 1.069, CC of 0.9951, and bias of 2.3 (6.2%).

Conclusion: These data indicate that contemporary cTnI AccuTnI+3 results above the 99th percentile URL are comparable with hs-cTnI results if both are tested on DXI 800, and hs-cTnI results tested on Access 2 and DXI 800 are comparable at levels less than 200 ng/L. Therefore, to use the Beckman Coulter cTnI assay properly, we suggest the laboratory report cardiac troponins with the assay and instrument names to reduce confusion during results comparison.