Laboratory Criteria of Antiphospholipid Syndrome Need to be Updated or Strictly Followed?

ABSTRACT

The antiphospholipid syndrome is a very relevant disease that implicates different clinical features and laboratory criteria. Regarding laboratory diagnosis, it has been established in the last consensus that tests included are lupus anticoagulant (LA), anti cardiolipin (aCL) and anti β₂ glycoprotein I antibodies (anti β₂GPI) of IgG or IgM isotype at medium to high titres. There is not one unique or a gold standard test for APS, so laboratory diagnosis is one of the more important problems. Considering LA testing, new guidelines have been recently published. They include not only the selection of coagulation tests, but also important recommendations about preanalytical variables, mixing and confirmatory studies interpretation, and cut off calculations. Taking into account solid phase assays, the major problem is the low reproducibility and the high inter assays variation. This problem has been recognized early with aCL. Despite many efforts such as the introduction of polyclonal and monoclonal standards, laboratory workshops, etc, the situation is still complicated. This problem was supposed to be solved when anti β₂GPI were introduced, but many collaborative studies and quality control surveys assessment have also demonstrated a lot of problems in standardization. The need of reference materials for LA and solid phase assays has been recognized many years ago but there is no clear advance in this line. Another important aspect is the fact that none of these tests are specific for APS, so they can be present in many clinical settings. Recent advances have been done by developing assays to detect anti domain I β₂GPI antibodies that could be more specific. It is hoped that in the near future, by worldwide collaborative actions, problems on laboratory diagnosis of APS will be overcome.

Keywords:

Antiphospholipid antibodies, lupus anticoagulant, anticardiolipin antibodies, antiphospholipid syndrome.