Role of antiphospholipid antibodies in kidney disease: Risk factors, immunopathogenesis, and diagnosis

Table 3 EULAR 2023 classification criteria for antiphospholipid syndrome

(1) Entry criterion:

A patient must have at least one positive aPL test (LAC, aCL IgG/IgM, or anti-β2GPI IgG/IgM) on two occasions at least 12 weeks apart

The positive test must be from a solid-phase assay validated for clinical use, and at least one test must be high-titer or persistent

(2) Additive weighted scoring:

Once the entry criterion is met, clinical and laboratory features are assigned points

A score of ≥ 10 points is required to classify a patient as having APS

Clinical criteria

Venous thromboembolism 4 points

Arterial thrombosis 5 points

Pregnancy morbidity

≥ 3 consecutive unexplained early miscarriages 3 points

≥ 1 unexplained fetal death after 10 weeks 4 points

Preterm birth due to eclampsia/HELLP/severe 3 points preeclampsia

Laboratory criteria

LAC - 4 points

High-titer aCL IgG or anti-β2GPI IgG - 3 points

Double or triple antibody positivity - 3 points

C3/C4 (suggesting complement activation) - 2 points

Classification as APS requires a total score of ≥ 10 points, combining laboratory and clinical features

aCL: Anticardiolipin antibody; aPL: Antiphospholipid antibody; APS: Antiphospholipid syndrome; β2GPI: Β2 glycoprotein I; EULAR: European League Against Rheumatism; HELLP: Hemolysis, elevated liver enzymes, and low platelets; IgG: Immunoglobulin G; IgM: Immunoglobulin M; LAC: Lupus anticoagulant.