Cardiac Troponin T Stability Study for Regulatory Approval of the 6th Generation High-Sensitivity Assay.

BACKGROUND: High-sensitivity cardiac troponin T (hs-cTnT) assays must meet strict criteria prior to regulatory approval, as the test is central to myocardial infarction diagnosis. Evaluating analyte stability is essential for ensuring accurate results in stored samples. Here, cTnT stability using the novel sixth-generation assay was evaluated. We also discuss regulatory complexity. METHODS: From patients with acute coronary syndrome, serum and lithium heparin plasma (Li-Hep) were collected, pooled per matrix, and aliquoted. One aliquot was immediately analyzed (fresh) while the remainder was stored at ≤-60°C. Selected aliquots were thawed and measured (fresh-frozen) before transfer to 15-25°C for 3 and 5 h, or 2-8°C for 11 and 24 h. Long-term aliquots were transferred frozen to -15 to -25°C for ≥13 months or ≤-60 for 9 and ≥13 months. Measurements were performed in quadruplicate using the Elecsys® hs-cTnT Gen 6 assay on a Cobas® Pure analyzer (Roche Diagnostics). Recovery was calculated relative to fresh measurements. Maximum permissible differences (MPD) were ±1.2 ng/L, ±20%, and ±15% for cTnT concentrations <6 ng/L, ≥6-≤24 ng/L, and >24 ng/L, respectively, allowing one exceedance per condition. RESULTS: In total, >2000 measurements were performed in 18 distinct samples per matrix. Median cTnT concentrations were 49.3 ng/L (8.4-782) in Li-Hep and 49.8 ng/L (8.5-822) in serum. The observed deviation in recovery was below the MPD for all storage conditions and acceptance criteria were met. CONCLUSIONS: Stability of cTnT using the sixth-generation hs-cTnT test was demonstrated across different storage conditions for serum and Li-Hep.