Performance of two new, automated chemiluminescence assay panels for anticardiolipin and anti-beta2-glycoprotein I antibodies in the laboratory diagnosis of the antiphospholipid syndrome.

INTRODUCTION: Anticardiolipin (aCL) and anti-ß2-glycoprotein I (aß2GPI) antibodies are two of the three laboratory criteria for antiphospholipid syndrome (APS). All assays for antiphospholipid antibodies (aPL), coagulation assays as well as ELISAs, show methodological shortcomings, which makes the search for better assays everlasting. The purpose of this study was to investigate the diagnostic performance of two new, fully automated systems (Zenit RA and HemosIL Acustar) applying chemiluminescent technology for aPL detection. METHODS: The study cohort consisted of a patient population presenting with thrombosis. In such patient population, the demonstration of aPL determines whether a patient has APS or not with implications for treatment. One hundred and twenty-four patients with thrombotic complications, of whom 26 were patients with definite APS, were integrated in this study. Besides, aPL titres were compared to the Sapporo standards. RESULTS: Results of both systems agreed well with ELISA and mutually. Analysis of the discrepant results between Zenit and Acustar finally led to one misclassification as APS. CONCLUSION: Diagnostic performances of both Zenit RA and HemosIL Acustar were comparable with odds ratios lower limits of CI of 5 for aß2 GPI IgG for Zenit and Acustar and 6 and 5 for aCl IgG on Zenit and Acustar, respectively. However, even with these new automated systems, titres differed largely between systems, especially for aß2 GPI IgG.

Evaluation of three commercial ELISA kits for anticardiolipin and anti-beta2-glycoprotein I antibodies in the laboratory diagnosis of the antiphospholipid syndrome.

INTRODUCTION: The laboratory criteria of the antiphospholipid syndrome (APS) include lupus anticoagulant (LAC), anticardiolipin antibodies (aCL) and anti-ß2glycoprotein I antibodies (aß2GPI) IgG or IgM. METHODS: We evaluated three commercial ELISAs for aCL and aß2GPI IgG and IgM: Asserachrom® ('Stago'), Bio-Rad ('BR') and the Bindazyme™ (the Binding Site, 'BS'). RESULTS: Results of all assays and of LAC were correlated with the clinical background (n=228). Sensitivity for Stago/BS/BR aCL IgG was 14%/15%/18%, for aCL IgM 1%/5%/4%, for aß2GPI IgG 9%/10%/17% and for aß2GPI IgM 4%/4%/3%. The specificity for Stago/BS/BR for all assays ranged from 86% to 98%. The positive predictive value (PPV) for Stago/BS/BR aCL IgG was 46%/52%/40%, for aCL IgM 8%/36%/19%, for aß2GPI IgG 70%/67%/45% and for aß2GPI IgM 23%/23%/20%. Combining LAC with aCL and aß2GPI antibodies increased the sensitivity (Stago/BS/BR IgG: 26%/27%/31%, IgM: 22%/21%/26%) and PPV (Stago/BS/BR IgG: 41%/46%/36%, IgM: 34%/40%/36%). Comparing the diagnostic power of the tests, only Stago/BS aß2GPI IgG had a Chi-square P-value lower than 0.05. The combination of LAC and IgG ELISAs of BS resulted in the lowest P-value (0.098) compared to the other combinations. CONCLUSION: All evaluated ELISAs are a practical tool in the laboratory diagnosis of APS. The diagnostic performance shows slight differences between the ELISAs from the different manufacturers.