Lot-to-lot variability of a high-sensitivity cardiac troponin I assay: clinical implications

Objectives: High-sensitivity cardiac troponin I (hs-cTnI) assays are pivotal for diagnosing acute coronary syndromes and implementing accelerated rule-in/rule-out algorithms in the emergency department (ED). This study assessed the analytical and clinical performance of the Mindray hs-cTnI chemiluminescent immunoassay in comparison with the assays routinely adopted at the University Hospital of Padova (AOUP; Access, Beckman Coulter) and at Bassano Hospital (ULSS7; Architect, Abbott). Particular attention was given to reagent and calibrator lot-to-lot variability and its potential clinical impact. Methods: The study included 400 ED patients with suspected myocardial injury (213 at AOUP [P1] and 187 at ULSS7 [P2]), yielding a total of 823 lithium-heparin plasma samples collected at baseline, 2 h, and, when available, at a third time point. Lot-to-lot comparability was examined in 424 samples using two reagent/calibrator lot combinations (R1/C1 and R2/C2) and further explored in 51 additional samples tested with four lot combinations. Results: Within-laboratory imprecision was 2.03 % at 2.45 ng/L and 2.25 % at 4.76 ng/L. Among patients discharged from ED, the proportion of baseline values exceeding the 99th percentile was lower with the Mindray assay (P1: 16.2 %, P2: 15.1 %) compared with routine methods (P1: 26.8 %, P2: 17.8 %). Furthermore, diagnostic agreement was higher with Architect than with Access (Cohen's kappa 0.93 vs. 0.77). Lot-to-lot comparison demonstrated excellent concordance between R1/C1 and R2/C2 (bias 0.73 %; kappa 0.98). Conclusions: The evaluated assay demonstrated robust analytical and clinical performance, together with excellent lot-to-lot stability. Nevertheless, ongoing surveillance of reagent and calibrator lot changes remains advisable to ensure sustained analytical consistency and clinical reliability.