Clinical Effect of Recalibration of the Roche Cardiac Troponin T Assay

Objective: To assess the effect of recalibration of the Roche 3rd-generation cTnT assay with recombinant human cardiac troponin T (cTnT) standards on clinical decision limits. Materials and Methods: Serum samples from 77 patients (66 ± 16 years) admitted to the coronary care unit were assayed using the 2nd- and 3rd-generation cTnT assays. Results: There was excellent agreement (r = 0.99 Spearman, 95% CI 0.99–1.0; p ≤ 0.0001, n = 153) between the 2nd- and 3rd-generation cTnT assays across the analytical range, but there was a curvilinear relationship between values. There was concordance between the 2nd- and 3rd-generation cTnT values in the range from 0 to 0.2 μg/l. Above 0.2 μg/l, however, there were increasing but predictable differences. Conclusion: There was no statistical difference between the 2nd- and 3rd-generation cTnT assays, demonstrated by a linear relationship below 0.2 μg/l. This confirms that the 3rd-generation assay was calibrated to that of the 2nd-generation assay in the range of 0–0.2 μg/l. The detection limit and upper reference limit of normal will be unaffected by this change in calibration. A non-linear relationship at higher 2nd-generation concentrations (0.2–25.0 μg/l) was observed. Clinical decision limits up to 0.2 μg/l, associated with increased cardiac risk, are unaffected by the assay calibration, but values greater than 0.2 μg/l are affected.