Laboratory Diagnosis of the Lupus Anticoagulant

OBJECTIVE: This review describes consensus guidelines and laboratory methods for diagnosing a lupus anticoagulant (LAC). BACKGROUND: A prolonged APTT due to the presence of a LAC is a frequent finding in the clinical laboratory in patients referred for preadmission testing. Accurate detection of the LAC can often be very challenging for the laboratory. While no single assay is specific for diagnosing a LAC, there is a combination of assays that can be used to improve laboratory diagnosis. METHOD: This review describes several assays used to detect a LAC; reviews consensus guidelines that influence the choice of assays by laboratories; and associated preanalytical variables that may lead to a missed diagnosis. CONCLUSION: A thorough understanding of the principles involved in LAC testing and preanalytical variables may lead to a more accurate diagnosis of the LAC. ABBREVIATIONS: aB2GPI - anti-B2 glycoprotein I, aCL - anti-cardiolipin, APLAs - antiphospholipid antibodies, BCSH - British Committee for Standards in Haematology, CLSI - Clinical and Laboratory Standards Institute, DOAC - direct oral anticoagulant, dRVVT - dilute Russell's viper venom time, ISTH-SSC - International Society for Thrombosis and Haemostasis – Scientific Standardization Committee, LAC - lupus anticoagulant, VKA - vitamin K antagonist, SCT - silica clotting time.