Absolute Versus Relative Changes in Cardiac Troponin T: Corresponding Cutoffs Based on Quantile Generalized Additive Models (QGAM)

Background: The diagnosis of myocardial injury/infarction (MI) mainly relies on relative changes in cardiac troponin. However, absolute change cutoffs provide greater diagnostic sensitivity. We determined the absolute changes in high-sensitive cardiac troponin T concentrations (abs.hs-cTnT) corresponding to the main relative cutoffs (rel.hs-cTnT), using a quantile generalized additive model (qgam). Methods: Plasma.hs-cTnT from patients selected with a time variation of 1 to 6 hours were collected over a 6year period. The abs.hs-cTnT- to-rel.hs-cTnT relationship was fitted using qgam, after ordered quantile-based normalization (OQN) to reduce the influence of extreme values. Results: The qgam regression curve was nonlinear. Classifying patients (n = 9,753) above the recommended rel.hs-cTnT and predicted abs.hs-cTnT cutoffs as positive, the MI diagnosis rates were similar, and more reliable using the OQN-transformed data-based qgam, as compared to the untransformed data-based one. Conclusions: Through an optimized qgam-based approach accounting for heavy-tailed distributions, absolute.hs-cTnT are provided for the corresponding relative.hs-cTnT cutoffs.