A-023 Evaluation of Interfering Substances in VITROS High-Sensitivity Cardiac Troponin I Assay

Abstract

Cardiac troponin is established as the primary and core biomarker for the diagnosis of myocardial infarction in the Fourth Universal Definition of Myocardial Infarction. Specifically, high-sensitivity cardiac troponin I (hs-cTnI) acts as a key indicator in diagnosing acute myocardial injury such as acute myocardial infarction (AMI), hs-cTnI test results directly guide the initiation and termination of emergency treatment regimens, which is pivotal for the early identification of myocardial infarction and improvement of patient prognosis,therefore,the test accuracy is critical to ensuring the clinical application value of cTnI. However, various endogenous and exogenous interfering substances, including hemolysis, lipemia, bilirubin and biotin, may induce spurious elevation or reduction in troponin assay results. A prospective study screened 8129 patients with positive hs-cTnI results and identified 15 cases of suspected false positives, of which 12 cases (80%) were ultimately confirmed to be affected by interference. As an ISO 15189-accredited laboratory, we evaluated the effects of common interfering substances on hs-cTnI assay results following the introduction of the VITROS 5600 analyzer, aiming to avoid hs-cTnI result deviations caused by common endogenous and exogenous interferences, which may lead to the risk of misdiagnosis and unnecessary invasive diagnosis and treatment in patients without myocardial injury. In accordance with WS/T 416 Guidelines for Interference Testing in Clinical Chemistry and CLSI EP07-ED3, human serum mixed samples with troponin I (TnI) concentrations of approximately 10 ng/L and 300 ng/L were prepared. Four endogenous substances (free bilirubin, conjugated bilirubin, hemoglobin and chylomicrons) from a commercial interference check Kit A and exogenous biotin reference materials were added to the above samples. The maximum interfering concentrations of all substances were determined in line with CLSI EP37-ED1 to prepare interfering substance stock solutions and blank control solutions. The VITROS 5600 analyzer was used for detection, and each sample with the maximum interfering concentration and the blank control sample were assayed in five replicates. The relative bias at the maximum interfering concentration was calculated using the formula below. A relative bias greater than 10% was defined as a significant interference of the substance on the assay results. Maximum relative bias = (Mean value of interference-added samples - Mean value of blank control solution) / Mean value of blank control solution × 100% Assays of the five interfering substances revealed that no deviation exceeding 10% was observed for all tested interfering substances in both low and high TnI concentration samples (at the nominal concentrations of 10.00 ng/L and 300.0 ng/L, respectively). For clinical laboratories, it is essential to clarify the interference thresholds of detection items when introducing a new testing system or a new assay. This facilitates the formulation of rational sample rejection criteria and prevents erroneous results from misleading clinical decision-making. This study confirms that the VITROS hs-cTnI assay exhibits favorable anti-interference capacity against common interfering substances, which can avoid unnecessary repeated blood sampling for patients and, more importantly, reduce the risk of misdiagnosis induced by interfering substances.