'Criteria' aPL tests: Report of a Task Force and preconference workshop at the 13th International Congress on Antiphospholipid Antibodies, Galveston, Texas, April 2010

Current classification criteria for definite antiphospholipid syndrome (APS) mandate the use of one or more of three positive 'standardized' laboratory assays to detect antiphospholipid antibodies (aPL) (viz: anticardiolipin [aCL] IgG and IgM; anti-β₂glycoprotein I [anti-β₂GPI] antibodies IgG and IgM; and/or a lupus anticoagulant [LAC]), when at least one of the two major clinical manifestations (thrombosis or pregnancy losses) are present. Although, efforts of standardization for these 'criteria' aPL tests have been conducted over the last 27 years, reports of inconsistencies, inter-assay and inter-laboratory variation in the results of aCL, LAC, and anti-β₂GPI, and problems with the interpretation and the clinical value of the tests still exist, which affect the consistency of the diagnosis of APS. A Task Force of scientists and pioneers in the field from different countries, subdivided in three working groups, discussed and analyzed critical questions related to 'criteria' aPL tests in an evidence-based manner, during the 13^th International Congress on Antiphospholipid Antibodies (APLA 2010, April 13-16, 2010, Galveston, TX). These included: review of the standardization and the need for international consensus protocol for aCL and anti-β₂GPI tests; the use of monoclonal and/or polyclonal standards in the calibration curve of those tests; and the need for establishment of international units of measurement for anti- β₂GPI tests. The group also reviewed the recently updated guidelines for LAC testing, and analyzed and discussed the possibility of stratification of 'criteria' aPL tests as risk factors for APS, as well as the clinical value of single positive vs. multiple aPL positivity. The group members presented, discussed, analyzed data, updated and re-defined those critical questions at a preconference workshop that was open to congress attendees. This report summarizes the findings, conclusions, and recommendations of this Task Force.