B-370 Toward the Standardization of Homocysteine Testing: A Metrological Framework Based on a Candidate Reference Method and Commutable Candidate Reference Materials

Abstract

Homocysteine (Hcy) is a critical biomarker for cardiovascular risk stratification. However, significant variability exists among routine detection methods in clinical laboratories across China, as evidenced by external quality assessment data, underscoring an urgent need for standardization to ensure reliable and comparable results. A candidate reference measurement procedure (cRMP) for serum Hcy was established using isotope-dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and rigorously validated. This cRMP served as an accuracy benchmark to evaluate five routine methods, encompassing various immunoassays and another LC-MS/MS platform. Furthermore, recalibration of these routine methods was performed using five human serum pools with values assigned by the cRMP. The developed ID-LC-MS/MS cRMP demonstrated excellent performance, with a limit of quantitation of 3.62 nmol/L, total imprecision <1% coefficients of variation, and a minimal bias of 0.48% against certified reference material SRM 1950. Method comparison revealed significant systematic biases across all routine methods (mean bias range: -9.09% to +54.19%), despite strong correlations (R² > 0.96). Recalibration using commutable human serum pools effectively corrected these biases, reducing the mean relative difference between each routine method and the cRMP to within -2.88% to 4.89%. This study establishes a high-accuracy cRMP for Hcy and demonstrates that commutable, value-assigned human serum pools are a potent tool for harmonizing disparate clinical detection systems. The findings provide a practical and traceable pathway toward improving inter-laboratory comparability and advancing standardization of Hcy testing.