Kidney Function-Specific Performance of High-Sensitivity Troponin T and I Using 0/1 h and 0/3 h Protocols in Suspected Non-ST-Segment Elevation Acute Coronary Syndrome

Background/Objectives: Impaired kidney function is associated with persistently elevated cardiac troponin levels, complicating evaluation of suspected non-ST-segment elevation acute coronary syndrome (NSTE-ACS). The comparative performance of high-sensitivity cardiac troponin T (hs-cTnT) and I (hs-cTnI) across sampling intervals in this population remains uncertain. We aimed to identify a kidney function-adapted assay-sampling protocol combination for suspected NSTE-ACS that may support collaborative pathways between nephrologists and acute care clinicians. We therefore assessed kidney function-specific diagnostic and prognostic performance using 0/1 h and 0/3 h protocols. Methods: We conducted a prospective observational cohort study of adults presenting with suspected NSTE-ACS at a tertiary emergency department between March 2019 and December 2020. Patients were stratified according to kidney function at presentation using estimated glomerular filtration rate (eGFR). Impaired kidney function was operationally defined as eGFR < 60 mL/min/1.73 m2. Serial hs-cTnT and hs-cTnI concentrations were measured at 0, 1, and 3 h and interpreted using assay-specific thresholds and delta criteria. Diagnostic performance for NSTE-ACS and prognostic performance for 30-day major adverse cardiovascular events (MACEs) were evaluated. Results: Among 140 patients, 58 (41%) had impaired kidney function. Baseline hs-cTnT and hs-cTnI concentrations were significantly higher in patients with impaired kidney function across all sampling time points. In this group, the 0/3 h protocol demonstrated superior diagnostic performance compared with the 0/1 h protocol for both assays. Using 0/3 h testing, hs-cTnI achieved the highest sensitivity (88.6%; 95% CI, 49.2–95.3), whereas hs-cTnT showed the highest negative predictive value (92.2%; 95% CI, 76.2–94.6). In patients with preserved kidney function, both assays demonstrated high specificity and positive predictive value with the 0/3 h protocol. Prognostic discrimination for 30-day MACEs also improved with a 0/3 h strategy, particularly in patients with impaired kidney function. Conclusions: In patients with impaired kidney function and suspected NSTE-ACS, extending troponin testing to 3 h improves diagnostic accuracy and short-term prognostic performance, supporting kidney function-adapted troponin strategies in emergency and nephrology care.