In order to determine the relationship between antiphospholipid antibodies(APLAs) and thromboembolic events (TEs) in children we performed a cross sectional cohort study of 59 consecutive children with systemic lupus erythematosus (SLE) managed at two major Canadian SLE clinics. In addition, children with Juvenile Rheumatoid Arthritis (JRA) and healthy children were studied as control populations. Patients were classified as TE positive(TE+ve) only when events were confirmed by objective tests. The presence of APLAs was determined by five reference coagulation assays for the lupus anticoagulant (LA) and by ELISA assay for both IgG and IgM anticardiolipin antibodies (ACLA). Patients were classified as APLA positive when one or more tests were positive on two separate occasions at least three months apart. None of the JPA control patients had TEs or were positive for APLA. In the SLE group a total of 13 objectively confirmed TEs occured in 10 patients. Four events were in in the deep venous system, 2 events were pulmonary emboli, 6 events involved the central nervous system and 1 patient had portal vein thrombosis. The relationship between TEs and APLA status is summarized below.Table 57% of children who were LA positive had a TE. There was a statistically significant association between the presence of LA and both arterial and venous TE in children with SLE. A non-significant trend between ACLAs and TEs was shown. This is the first report of a marker associated with TEs in children. Randomized controlled trials are needed to determine appropriate prophylactic therapy in these children.

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