Diagnosing Antiphospholipid Antibody Syndrome: A Review of the Criterion for Definite APS

Antiphospholipid Antibody Syndrome (APS) is a highly prevalent cause of antibody-mediated thrombosis manifesting in venous thrombosis (DVT and PE), arterial thrombosis (most commonly stroke), and pregnancy complications. The diagnosis of definite APS requires both clinical and laboratory criterion as established by the working group of the International Congress on Antiphospholipid Antibodies (based on expert opinion). Since thrombosis and pregnancy loss are common in the general population, and antiphospholipid antibodies (aPL) occurs in a small percentage of the healthy public, it is important to demonstrate antibody persistence in patients who have the proper clinical indications in order to avoid misdiagnosis. Unfortunately, laboratory testing in this area lacks standardization, resulting in wide inter-laboratory variance. However, due to the commercialization of tests and automation, inter-laboratory variance has improved. Data on several new non-criterion tests suggest that they may improve the specificity or risk stratification for thrombosis. A new guidance document on aPL testing strives to achieve better consistency, but much work remains to be done in the area of standardization.