Antiphospholipid IgG Certified Reference Material ERM®-DA477/IFCC: a tool for aPL harmonization?

Objectives: The Certified Reference Material (CRM) ERM®-DA477/IFCC is a new polyclonal IgG anti-beta2 glycoprotein I (anti-β2GPI) material for the harmonization of the laboratory diagnosis of antiphospholipid syndrome (APS). We evaluated CRM`s ability to represent the heterogeneity of APS patient anti-β2GPI antibodies and to calibrate IgG anti-β2GPI methods. Methods: We characterized CRM for its reactivity against domain-1, using the QUANTA Flash® β2GPI-domain-1 assay, and against domains-4-5 of β2GPI, and single-domain-deleted β2GPI molecules using in-house ELISAs. We used QUANTA Lite® ELISA, QUANTA Flash® CLIA, and EliA FEIA methods to evaluate the CRM`s anti-Cardiolipin (anti-CL) activity. Four anti-β2GPI IgG methods (in-house and QUANTA Lite® ELISA, QUANTA Flash® CLIA, and EliA FEIA) were also used to evaluate the CRM`s calibration efficacy, alongside 133 clinical samples (CSs) and 99 controls. Results: The CRM showed high anti-domain-1 activity and no anti-domain-4-5 activity at the recommended assay dilution. The domain-dependent-β2GPI reactivity profiles were comparable with full-blown APS. There was acceptable dilution linearity for anti-CL assays with R2 ranging from 0.957 to 0.997. For the four anti-β2GPI IgG assays, calibration with the CRM led to a good comparability of the average result of CSs for two of the assays. New cut-offs calculated from this work improved comparability in quantitative results between three of the assays: 85% concordance with CRM compared to 66% concordance with assay-specific-calibration. Conclusions: The CRM is representative of patient anti-β2GPI/CL heterogeneity and should improve anti-β2GPI IgG method harmonization. However, the level of achievable method harmonization is affected by differences in the selectivity among the assays.

GROSSI Claudia;  DEPREZ Liesbet;  BODIO Catarina;  BORGHI Maria Orietta;  KUMAR Suresh;  POZZI Nicola;  MACOR Paolo;  PIANTONI Silvia;  TINCANI Angela;  RADIN Massimo;  SCIASCIA Savino;  MARTOS Gustavo;  MONOGIOUDI Evanthia;  ZEGERS Ingrid;  SHELDON Joanna;  WILLIS Rohan;  MERONI Pierluigi; 

2025-11-28

WALTER DE GRUYTER GMBH

JRC140993

1437-4331 (online),   

https://www.degruyterbrill.com/document/doi/10.1515/cclm-2025-0032/html,    https://publications.jrc.ec.europa.eu/repository/handle/JRC140993,   

10.1515/cclm-2025-0032 (online),