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Updated: Aug 5, 2026
The ChroP Approach Combines ChIP and Mass Spectrometry to Dissect Locus-specific Proteomic Landscapes of Chromatin
Published on: April 11, 2014
From analytical bias to threshold-based discordance: An ID-LC-MS/MS reference method reveals and corrects
Kaiduo Xu1, Yunmiao Sun2, Xuanchang Bai1
1National Center for Clinical Laboratories, Beijing Engineering Research Center of Laboratory Medicine, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, China.
Background:
Homocysteine (Hcy) is a critical biomarker for cardiovascular risk stratification, but significant between-method variability in China can result in classification discordance relative to candidate reference measurement procedure (cRMP), including both positive discordance and negative discordance of hyperhomocysteinemia. We aimed to establish a cRMP and evaluate its ability to correct method-dependent classification discordance.
Methods:
An isotope-dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) cRMP for serum Hcy was developed and validated. Five routine methods were evaluated against this cRMP using 59 individual patient samples. Classification concordance with the cRMP was assessed before and after recalibration using threshold-based classification of 15 and 30 μmol/L.
Results:
The cRMP showed total imprecision <1% CV and bias of 0.48% against SRM 1950. Pre-recalibration mean biases ranged from -9.09% to +54.19%. At the 15 μmol/L threshold, the Siemens assay showed classification discordance in 23.7% of samples (all positive discordance), and the Snibe assay in 6.8% (all negative discordance). After recalibration, these rates decreased to 1.7% and 0%, respectively. At the 30 μmol/L threshold, discordance was more widespread (Siemens 25.4% positive discordance; Strong/Roche 5.1% negative discordance each), but recalibration improved concordance rates for all methods (e.g., Siemens from 74.6% to 98.3%). The remaining methods achieved 100% correct at 15 μmol/L, but all showed some residual classification discordance at 30 μmol/L after recalibration.
Conclusion:
The cRMP combined with commutable human serum pools effectively corrected threshold-based discordance caused by systematic bias. This practical standardization pathway demonstrates potential clinical utility by improving the reliability of hyperhomocysteinemia classification relative to a higher-order reference.
