Joseph Rigano¹

¹Department of Haematology, Northern Health, Melbourne, Australia

Antiphospholipid syndrome (APS) is characterised by the persistent detection of antiphospholipid antibodies (aPLs). Lupus anticoagulant (LA) is one of the three criteria aPLs used in the laboratory identification of APS. Two phospholipid dependant assays utilising different principles should be used to detected LA. One being dRVVT and the other a LA sensitive aPTT both paired with low and high phospholipoid concentration. Initial prolonged screening assays should be followed up with mixing and confirmatory assays. Often testing is requested when patients are anticoagulated leading to interference with false positive and false negative results. To overcome anticoagulant interference, commercial DOAC removal agents are available in the form of activated charcoal and filters. Alternatively, Taipan snake venom time/ecarin time (TSVT/ET) can be used in patients on VKA and anti-Xa DOACs. Interpretation of LA testing is dependant on cut-off values which should be established in each laboratory based on reagent and instrument combination. Repeat testing should be performed to exclude transient antibodies produced by infection and drugs and elevated acute phase proteins yielding equivocal results. Results should be reported as positive (presence) or negative (absence) for LA. Re-testing should be performed on a second occasion 12 weeks from initial LA detection to confirm persistent positivity.