Assessment of agreement of two high sensitivity troponin assays during an institutional transition

Aim: During a recent institutional transition between two high sensitivity troponin assays, we sought to evaluate the correlation and agreement in an unselected population presenting to the ED undergoing troponin measurement. Methods: This was a prospective study of consecutive patients presenting to a single, academic institution that underwent troponin testing. Paired samples of two high sensitivity troponin assays, hs-cTnT (Gen 5 TnT; Roche Diagnostics, Indianapolis, IN) and hs-cTnI (High Sensitive Troponin I Architect i2000; Abbott, Abbott Park, Illinois) were assessed for overall correlation and agreement. We also evaluated the paired difference between the two assays stratified by gender and CKD stage. Further, we determined reclassification at the 99th percentile limit and the institutional established abnormal. Results: A total of 1349 unique patient encounters were included in the study with median result value of 12.2 ng/L (IQR 6-29.5) for hs-cTnT and 4.7 ng/L (IQR 3.5-15.5) for hs-cTnI. Direct comparison of the two assays indicated a Spearman Rho of 0.79 with poor agreement especially when cTn results were elevated. Paired difference was smaller in women with a difference of medians of 0.9 ng/L (0.06-1.67, P < 0.01) and three significant clusters (CKD 1, CKD 2 and 3, CKD 4 and 5; P < 0.01) were found when stratifying by Chronic Kidney Disease stage Reclassification occurred in 276 patients when evaluated at the 99th percentile and 148 patients at the institution’s abnormal cut-off. Conclusion: There was moderate correlation seen during our transition between the two high sensitivity troponins, but differential bias with lower hs-cTnI than hs-cTnT at low levels and higher hs-cTnI than hs-cTnT at high values. Without the appropriate system level recommendations and established diagnostic protocol this level of disagreement can potentially cause problems with interpretation to the end clinician who has become accustomed to a specific assay’s thresholds.