How to use… lupus anticoagulants

Lupus anticoagulants (LA) were first detected in patients with systemic lupus erythematosus (SLE) in 1952 by Conley and Hartmann.1 They identified patients in whom the activated partial thromboplastin time (APTT) was prolonged and which did not correct on the addition of normal plasma. Although Conley and Hartmann's original description was in association with a haemorrhagic disorder, subsequent reports from the 1960s highlighted patients with thrombotic events in the presence of LA.2 The term ‘lupus anticoagulant’ was introduced by Feinstein and Rapaport in 1972.3 It has, however, caused some confusion because LA tend to be procoagulant in vivo, and most people who test positive for LA do not meet criteria for a diagnosis of SLE.4 LA are a subset of antiphospholipid antibodies (aPL) which also include anticardiolipin antibodies (aCL) and anti-β2 glycoprotein-I (anti-β2GPI) antibodies among others. The clinical significance of these antibodies is their association with venous or arterial thrombosis, or recurrent fetal loss. This association constitutes the antiphospholipid antibody syndrome (APS) for which there are revised classification criteria published in 2006.5 Some features not included in the classification criteria are associated with APS and are more commonly seen in children than adults. These include immune-mediated thrombocytopenia, haemolytic anaemia, migraine, chorea and epilepsy.6 This paper aims to highlight which children should be tested for LA, and the significance of LA if they are detected. LA are a mixture of different immunoglobulins (IgG and IgM) that bind to various protein-phospholipid complexes.4 Targets include β2GPI, prothrombin, protein C and S and factor XI among others.7 In common with other antibodies, LA are produced by B lymphocytes. In the context of SLE, there is a generalised increase in production of autoantibodies. The reasons for production of LA in other contexts are …