Matrix-matched low-concentration internal quality control detects high-sensitivity cardiac troponin T errors missed...

High-sensitivity cardiac troponin T (hs-cTnT) is a cornerstone biomarker for diagnosing acute coronary syndrome (ACS), utilizing the 99th percentile upper reference limit (URL) as the key diagnostic threshold. However, most commercial quality control (QC) materials lack coverage at this low concentration, potentially compromising assay monitoring at clinically decisive levels. This study aimed to prepare a stable, cost-effective pooled serum internal quality control (IQC) material targeting the 99th percentile URL of hs-cTnT and evaluate its feasibility for routine QC monitoring. A low-concentration IQC was prepared from pooled patient serum with homogeneity and stability assessed according to established protocols. Its performance was compared to commercial medium- and high-level QCs in detecting simulated calibration shifts, followed by a 12-month implementation in daily practice alongside commercial controls. A cost analysis was conducted in parallel. Results indicated that the self-made IQC exhibited good homogeneity and long-term stability, with a total coefficient of variation of 4.1% over 12 months. Crucially, it detected simulated calibration errors more effectively than commercial controls. During routine monitoring, it identified two clinically significant out-of-control events missed by commercial materials. Adopting this self-made QC yielded an annual net saving of approximately ¥13,737, representing a 71.1% cost reduction for our laboratory. In conclusion, a self-prepared low-concentration IQC from pooled serum offers a stable, and cost-effective complement to commercial QC materials for hs-cTnT monitoring at the 99th percentile URL. This approach helps laboratories enhance quality assurance at clinically critical low concentrations, supporting the analytical reliability of hs-cTnT results used in ACS diagnosis.