• DevreeseKatrien M JKMJ and Denis Wahl.
• Pol. Arch. Med. Wewn. 2024 Sep 24.

AbstractThis paper focuses on the laboratory tests necessary for the diagnosis of antiphospholipid syndrome (APS). Diagnosis starts with the selection of patients suspicious of having APS. The timing related to the clinical event is important to avoid false classification of APS patients. For the interpretation of the test results of antiphospholipid antibodies (aPL) understanding of all pitfalls and interferences is necessary. Lupus anticoagulant (LA) measurement remains a complex procedure with many pitfalls and interferences. The effect of anticoagulant therapy, the main confounder of LA measurement, can be overcome by removal agents for direct oral anticoagulants (DOAC) or by considering assays as Taipan snake venom time / Ecarin clotting time not affected by antivitamin K therapy and anti-Xa DOAC. However, both procedures have limitations. Solid-phase assays for anticardiolipin antibodies (aCL) and anti-β2-glycoprotein 1 antibodies (aβ2GPI) show inter-assay differences. Diagnosis is based on the measurement of three groups of aPL: LA, aCL and aβ2GPI, of IgG and IgM isotype. This allows to make antibody profiles that helps in identifying patients at risk. Other aPL, such as antibodies against the domain I of β2GPI and anti-phosphatidylserine-prothrombin antibodies may be useful in risk stratification of APS patients and in some specific situations of patients with incomplete antibody profile, but are not needed for diagnosis. Laboratory diagnosis of APS remains challenging. To increase the diagnostic efficacy and reliability, an integrated interpretation of all results and an interpretative comment should be provided on the laboratory report. Therefore, a close interaction between clinical pathologists and clinicians is mandatory.

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