April 04/14: IgA antiphospholipid antibodies – more relevant in Primary Antiphosholipid Syndrome
- IgA anti-β2GP1 was significantly associated with thrombosis in PAPS
- Isolated IgA anti-β2GP1 was present in 10.6% of otherwise seronegative patients.
Mattia,E.; Ruffatti,A.; Tonello,M.; Meneghel,L.; Robecchi,B.; Pittoni,M.; Gallo,N.; Salvan,E.; Teghil,V.; Punzi,L.; Plebani,M.
IgA anticardiolipin and IgA anti-beta2 glycoprotein I antibody positivity determined by fluorescence enzyme immunoassay in primary antiphospholipid syndrome
Clin Chem.Lab Med. 2014 doi: 10.1515/cclm-2014-0039
Background: Antiphospholipid syndrome (APS) may be classified as primary (PAPS) if there is no evidence of underlying disease or secondary if it is associated with other diseases (particularly SLE). Laboratory criteria for APS classification include Lupus anticoagulant (LA), medium-high levels of IgG/IgM anticardiolipin antibodies (aCL) and medium-high levels of IgG/IgM anti-β2 glycoprotein 1 antibodies (anti-β2GP1). The relevance of IgA aPL antibodies is controversial and they are not included in the recommended laboratory criteria.
Summary: Samples from 84 PAPS patients, 66 seronegative patients (with clinical manifestations of PAPS but negative results for IgG/IgM aCL and anti-β2GP1 and 78 healthy blood donors were assessed for levels of IgA aCL and IgA anti-β2GP1 as well as IgG, IgM levels and the presence of LA. IgA aCL was present in 19% of the PAPS patients while IgA anti-β2GP1 was present in 50% of them. The mean titers of both were higher in the thrombotic patients but only the latter were significantly associated with thrombosis. Isolated IgA anti-β2GP1 positivity was significantly present in 10.6% of the seronegative patients. The frequency of IgA aCL and anti-β2GP1 antibodies was similar to those of IgM aCL and IgM anti-β2GP1 respectively but the IgA isotype had a higher prevalence in the thrombotic PAPS group.
Conclusions: The study substantiates the clinical relevance of IgA anti-β2GP1 antibodies which were associated with thrombosis, the most severe feature of PAPS and to a triple aPL profile that is linked to the highest clinical risk. These antibodies could be considered a potential diagnostic tool for PAPS.
Comment: This study adds to previous work suggesting a higher clinical value of the presence of IgA antibodies in patients with clinical signs and symptoms of APS than previously thought. If these patients do not meet conventional antiphospholipid antibody laboratory criteria, it may well be worthwhile assessing them for IgA anti-β2GP1 antibodies. If these results are confirmed by other studies, IgA anti-β2GP1 could be included in the laboratory criteria for APS classification.
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