Abstract Number: PB1067
Meeting: ISTH 2021 Congress
Background: Anti-phospholipid (APL)-syndrome (APLS) is characterized by presence of both: specific clinical events that include vascular-thromboemboli and/or adverse-pregnancy-outcomes; and persistent abnormal clinical laboratory (i) serologic-tests which include elevated serum levels of one or more anti-phospholipid (APL)-antibodies such as IgM-/IgG-anti-cardiolipin (ACL)-antibodies and IgM-/IgG-anti-β2-glycoprotein-I (aβ2GPI)-antibodies, and/or (ii) coagulation-assays for lupus anticoagulant (LA) . Specificity and sensitivity of laboratory assays for detecting APL-antibodies should be sufficiently high to render accurate diagnoses and optimal medical-outcomes. The most frequently used platform is presently the enzyme-linked-immunosorbent-assay (ELISA), which detects/quantifies antibodies against a single antigen, novel tests like the addressable-laser-bead-immunoassay (ALBIA), which measures antibodies against multiple antigens, are increasingly being performed.
Aims: Describe a single Center’s experience with laboratory platform discrepancy between standard and novel technology for aCL IgM antibody.
Methods: Retrospective record review of two unrelated females—33-y/o with a first-trimester pregnancy loss & 42-y/o with left renal artery thrombosis—were found to have isolated markedly & moderately elevated IgM-ACL-antibody titers, respectively, by ELISA (QUANTA Lite), but within-reference-range titers by ALBIA (BioPlex™ 2200). The tests for other APL-antibodies and LAs were within-reference-range.
|Case||IgM ACL (ELISA)||IgM ACL (ALBIA)|
|33 y/o Female||105 MPL||2.2 MPL|
|102 MPL||2.4 MPL|
|42 y/o Female||82 MPL||4.2 MPL|
|53 MPL||3.7 MPL|
>40-80 MPL Medium (Diagnostic)
>80 MPL High Titer (Diagnostic)
Results: APLS-diagnosis requires repeat APL-antibody testing which different assay-platforms are now available. As decisions concerning antithrombotic-therapy and/or prophylactic-anticoagulation are based on accurate diagnosis, clinical-practice-issues arise with discrepant-laboratory results. As described for these 2 cases, isolated IgM-ACL-antibody elevations were noted with the widely-used singleplex-ELISA but not with the recently introduced multiplex-ALBIA-immunoassay. Unclear if : 1) elevated ELISA-titers are due to inadequate specificity with this platform (i.e., non-specific ACL-antibody binding to immobilized-cardiolipin capture-molecules); or 2) within-reference-range ALBIA-titers are due to an inadequate sensitivity, i.e. due to distinct assay-design feature(s).
Conclusions: Since diagnosis of the APLS requires persistent-positivity of at least one of the specific-laboratory-tests for APL-antibodies, it is clear from the current patients with isolated elevated IgM-ACL-antibodies that further study is needed to determine which of these assay-platforms is biologically-accurate.
To cite this abstract in AMA style:Escobar M, Howard TE, Montanez N. Laboratory Testing Platform Discrepancy between Current Singleplex-assay and New Multiplex-assay for Detecting and Quantifying IgM-anti-Cardiolipin-antibodies and other Anti-Phospholipid (APL)-antibodies: The Potential for Mis-diagnosis of the APL-syndrome [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/laboratory-testing-platform-discrepancy-between-current-singleplex-assay-and-new-multiplex-assay-for-detecting-and-quantifying-igm-anti-cardiolipin-antibodies-and-other-anti-phospholipid-apl-antibod/. Accessed December 5, 2021.
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