Long forms of cardiac troponin T are independent of kidney function and improve the diagnosis of myocardial infarction

BACKGROUND AND HYPOTHESIS: A recently developed cardiac troponin T (cTnT) assay measuring intact or mildly fragmented cTnT (long cTnT) has shown promise in improving the accuracy of myocardial infarction (MI) detection compared to the commercial high sensitivity cTnT (hs-cTnT) assay. However, data on patients with kidney dysfunction are limited. We compared the performance of long and hs-cTnT in MI diagnostics across the full spectrum of kidney function. METHODS: In this prospective study, consecutive patients presenting at the emergency department with an elevated (≥14 ng/L) hs-cTnT were recruited. Long and hs-cTnT were measured on admission and kidney function was determined with plasma creatinine (Crea), cystatin C (CysC) and estimated glomerular filtration rate (eGFR) using contemporary equations with Crea, CysC or both (Crea-CysC) together. The association of eGFR with hs-cTnT and long cTnT concentrations and the discriminative ability of hs-cTnT and long cTnT for type 1 MI and any MI were evaluated. RESULTS: In total, 1811 patients were included, 205 (11.3%) had a MI and 204 (11.3%) had a history of chronic kidney disease. The overall median (interquartile range) Crea-eGFR, CysC-eGFR and Crea-CysC-eGFR were 71 (51-87), 52 (36-69) and 63 (44-79) ml/min/1.73m2. In patients without MI, long cTnT showed no consistent association with kidney function (β=0.0008, P = 0.050; β=0.0005, P = 0.222; β=0.0006, P = 0.182 for Crea-eGFR, CysC-eGFR and Crea-CysC-eGFR, respectively), whereas hs-cTnT was inversely associated with kidney function (β=-0.0032, -0.0035 and - 0.0035; all P < 0.001). Long cTnT demonstrated superior diagnostic performance compared with hs-cTnT for the detection of MI (P < 0.001), with the advantage becoming progressively more pronounced with lower eGFR irrespective of equation used. CONCLUSIONS: In contrast to hs-cTnT, long cTnT is unaffected by kidney function and outperforms hs-cTnT in the detection of MI, with the greatest diagnostic advantage observed in patients with lower eGFR.