Prevalence of clinically meaningful antiphospholipid antibodies in patients with systemic lupus erythematosus varies by race and ethnicity

The presence of antiphospholipid antibodies (aPLs), highly pathogenic autoantibodies that may trigger thrombosis and serious pregnancy complications, can influence the course of systemic lupus erythematosus (SLE) and contribute to organ damage.1 2 Reports of the frequency of aPLs in patients with SLE are highly variable, ranging from 11% to 86% of patients, but generally quoted as 25%-40%.3 4 Determination of the prevalence of aPLs is challenged by lack of standardisation of assays to measure lupus anticoagulant (LAC) and lack of standardisation of cut-off values in reports of aPL positivity for anti-cardiolipin (aCL) and anti-β2 glycoprotein I antibody (aβ2GPI) assays. Some reports include any positive aPL test (values >95th percentile), whereas others include only clinically meaningful aPL results (moderate-To-high titres) defined by international guidelines and considered strongly associated with clinical manifestations.4 Criteria for classification of antiphospholipid syndrome (APS) consider only moderate-To-high titre aPL antibodies (≥40 GPL/MPL units) and/or the presence of LAC.4 5 Moderate-To-high titres of antibodies alone provide a strong basis for risk stratification,4 5 whereas low titres do not. Race and ethnicity influence prevalence, manifestations, disease activity and severity of SLE and have been associated with some autoantibodies.6 Yet, accurate assessment of the prevalence of clinically meaningful aPL antibodies in diverse SLE populations is lacking.