Development and commutability assessment of serum-based candidate reference materials for homocysteine and their...

Elevated serum homocysteine (HCY) is associated with cardiovascular and other systemic risks. This study aimed to develop serum-based secondary candidate reference materials (Can-RMs) for metrological traceability and validating their dual utility as commutability-verified materials for external quality assessment (EQA).

First, 41 fresh serum samples were analyzed by isotope dilution liquid chromatography-tandem mass spectrometry reference method and four routine detection systems to evaluate baseline comparability. Second, the commutability of Can-RMs, EQA materials spiked with purified reference standards (Sta-EQA materials), and in-house prepared EQA materials with serum matrix (Ser-EQA materials) was assessed via Deming regression and bias analysis. Third, the commutable Can-RMs were deployed in a 62-laboratory EQA program; performance (CV, bias, total error) were evaluated per biological variation-based minimum analytical quality specifications (6.23%, 12.94%, and 23.21%).

Routine systems exhibited positive proportional biases (0.5%-13.1%) versus the reference method. The Can-RMs (L1-L5) and Ser-EQA materials were commutable across all systems (with only Can-RM L1 for the Leadman system was inconclusive under IFCC criteria). All Sta-EQA materials were non-commutable under both approaches. In the EQA program, the average laboratory pass rates for TE, bias, and CV were 91%, 87%, and 98%, respectively, with the Roche and Strong Biotechnologies systems achieving 100% pass rate.

In-house prepared serum-based Can-RMs and Ser-EQA materials exhibit excellent commutability, supporting reliable standardization assessment and accurate trueness validation for clinical procedures. A major limitation is that all reagents were tested on a single Roche Cobas c701 analyzer; future multi-instrument trials are required to verify generalizability.