Sample matrix and high-sensitivity cardiac troponin I assays

• Published in: Clinical chemistry and laboratory medicine Vol. 57; no. 5; pp. 745 - 751
• Main Authors: Kavsak, Peter A., Roy, Chantele, Malinowski, Paul, Clark, Lorna, Lamers, Shana, Bamford, Karen, Hill, Stephen, Worster, Andrew, Jaffe, Allan S.
• Format: Journal Article
• Language: English
• Published: Germany De Gruyter 24.04.2019; Walter De Gruyter & Company
• Subjects: analytical variation; Anticoagulants; Assaying; Blood Chemical Analysis - standards; Blood Specimen Collection; Calcium-binding protein; Edetic acid; Edetic Acid - chemistry; EDTA plasma; Ethylenediaminetetraacetic acids; Heart; Heparin; Heparin - chemistry; high-sensitivity cardiac troponin; Humans; Immunoassay - standards; Lithium; lithium heparin plasma; matrix; Plasma; Quality Control; Reference Values; Sensitivity; serum; Slope stability; stability; Stability analysis; Storage; Storage conditions; Troponin; Troponin I; Troponin I - blood; lithium heparin plasma; EDTA plasma; analytical variation; matrix; serum; high-sensitivity cardiac troponin; stability
• ISSN: 1434-6621; 1437-4331
• DOI: 10.1515/cclm-2018-1100

Background Manufacturers of high-sensitivity cardiac troponin (hs-cTn) assays have restricted use of what sample types or matrices are acceptable to use for measurement. Our goal was to evaluate the comparability of the Siemens ADVIA Centaur hs-cTnI assay across different matrices and under different storage conditions. Methods Three different QC-plasma matrices were evaluated for imprecision <10 ng/L. Passing-Bablok regression and difference plots were determined for cTnI concentrations spanning the reference interval (limit of quantification to male 99th-percentile: 2.5 ng/L to <60 ng/L) between serum and lithium heparin plasma, lithium heparin and EDTA plasma and between the Siemens and Abbott hs-cTnI assays. Stability at room temperature (RT) and 2-8 °C was also assessed across the three matrices. Results Over 16-weeks the SDs were ≤1.0 ng/L for QCs ranging from 5.0 to 8.3 ng/L. Across the reference interval there was excellent agreement between lithium heparin plasma and serum for the Siemens hs-cTnI assay (slope=0.98/intercept=-0.1), however, cTnI concentrations were proportionally lower in EDTA as compared to lithium heparin plasma (slope=0.90, 95% CI: 0.88-0.92). In lithium heparin plasma the Siemens hs-cTnI concentrations were higher than the Abbott hs-cTnI concentrations (slope=1.26/intercept=-0.2). Stability of cTnI in lithium heparin plasma as compared in serum and EDTA plasma appeared more labile, with decreases ≥20% in concentrations evident as early as 1-day in storage at RT. Conclusions There is excellent agreement in concentrations between lithium heparin plasma and serum with the Siemens ADVIA Centaur hs-cTnI assay; however, cTnI concentrations in EDTA plasma are lower. Reference intervals and clinical studies in EDTA plasma for the Centaur hs-cTnI assay are required before clinical use.