Technical Note: Comparison of Cardiac Troponin I Levels in Serum and Sodium-Citrate Plasma Using the ACCESS 2 Immunoassay

The aim of this study was to determine if sodium-citrate plasma is a suitable substitute for serum for cardiac troponin I (cTnI) measurement using the Beckman ACCESS 2 immunoassay. Linear regression analysis of cTnI levels in paired serum and sodium-citrate plasma samples from 80 patients provided a y- intercept of -0.0193 and a slope of 1.044. The correlation was good (r = 0.995; 95% confidence interval 1.017 to 1.068, p <0.0001). The paired results were not significantly different by Student's t-test. Serum and sodium-citrate plasma appear to be interchangeable as samples for cTnI measurement using the ACCESS 2 assay. Furthermore, the use of plasma reduces the turnaround time and may avoid false positive cTnI results due to residual fibrin. 453