Research paper Detection of antiphospholipid antibodies by automated chemiluminescence assay Antonella Capozzi, Emanuela Lococo, Maria Grasso, Agostina Longo, Tina Garofalo, Roberta Misasi, Maurizio Sorice ⁎ Dipartimento di Medicina Sperimentale, “Sapienza” University, Rome, Italy article info abstract Article history: Received 15 December 2011 Received in revised form 29 February 2012 Accepted 29 February 2012 Available online 6 March 2012 The laboratory diagnosis of antiphospholipid antibody syndrome (APS) requires the demon- stration of antiphospholipid antibodies (aPL) by lupus anticoagulant (LAC) measured through coagulation assays, anticardiolipin IgG or IgM antibodies (aCL) and/or anti-β2-glycoprotein I IgG or IgM antibodies (anti-β2-GPI), usually detected by ELISA. In this study we tested aCL by a new automated system using the chemiluminescence principle. Our results showed that, while almost all the sera from APS patients, positive for IgG aCL and anti-β2-GPI by ELISA, were also positive for IgG aCl by chemiluminescence, only 30.13% of pa- tients without clinical manifestations of APS, but positive for aCL and persistently negative for anti-β2-GPI (by ELISA) and LA, confirmed the positive test by chemiluminescence. This differ- ence was highly significant (p b 0.0001). Interestingly, this test also prompted to identify 20% of patients positive for LA, but persistently negative for both aCL and anti-β2-GPI IgG (ELISA). Thus, the new technology of automated chemiluminescence assay for measuring aPL may rep- resent an useful tool to identify “true” APS patients. © 2012 Elsevier B.V. All rights reserved. Keywords: Antiphospholipid syndrome Anticardiolipin antibodies Anti-beta2 glycoprotein I antibodies Lupus anticoagulant Thrombosis Zenit RA analyzer 1. Introduction In the last few years sensitive techniques have been developed for detecting various “antiphospholipid” anti- bodies (aPL), among which anticardiolipin antibodies (aCL) are the best characterized. aCl were first detected in sera of patients with systemic lupus erythematosus (SLE) or related autoimmune disorders. These autoantibodies are considered responsible for the so-called antiphospholipid antibody syn- drome (APS), which is characterized by arterial and/or ve- nous thromboses and multiple abortions (Hughes, 1985; Hughes et al., 1986). Diagnosis of APS requires the combina- tion of at least one clinical and one laboratory criterion (Wilson et al., 1999; Miyakis et al., 2006). aCL and anti-β 2 - glycoprotein-I (anti-β 2 -GPI) antibodies, detected by enzyme linked immunosorbent assay (ELISA) and the lupus anticoag- ulant (LA), detected by clotting assays, are the recommended tests for the detection of aPL (Tincani et al., 1998; Bertolaccini et al., 2005). Indeed, aPL represent a heterogeneous family of antibodies that react with serum phospholipid-binding plas- ma proteins, among which β 2 -GPI represents the main pro- tein cofactor (Galli et al., 1993; De Laat et al., 2004). In addition, protein S (Sorice et al., 1994a, 1996), protein C (Oosting et al., 1993), prothrombin (Arvieux et al., 1995; Sorice et al., 1998), annexin V (Kaburaki et al., 1997), annexin II (Salle et al., 2008) or vimentin (Ortona et al., 2010) have been also demonstrated as antigenic targets for these autoan- tibodies. “Pure” aPL can be detected by thin layer chromatog- raphy (TLC) immunostaining (Sorice et al., 1994b). Subsequent studies revealed that aCL may occur in a wide range of other conditions, including mainly infectious dis- eases, but also neurological disorders, treatment with particu- lar drugs or in apparently healthy individuals (Devreese and Journal of Immunological Methods 379 (2012) 48–52 ⁎ Corresponding author at: Dip. Medicina Sperimentale, “Sapienza” University of Rome, viale Regina Elena 324, 00161 Rome, Italy. Tel.: +39 6 49972675; fax: + 39 6 4456229. E-mail address: maurizio.sorice@uniroma1.it (M. Sorice). 0022-1759/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jim.2012.02.020 Contents lists available at SciVerse ScienceDirect Journal of Immunological Methods journal homepage: www.elsevier.com/locate/jim