Vol.16 No.3

ORIGINAL ARTICLE

Significance of antiprothrombin antibodies in patients with systemic lupus erythematosus: clinical evaluation of the antiprothrombin assay and the antiphosphatidylserine/prothrombin assay, and comparison with other antiphospholipid antibody assays

Authors

Akito Tsutsumi1 , Taichi Hayashi1, Yusuke Chino1, Mizuko Mamura1, Daisuke Goto1, Isao Matsumoto1, Satoshi Ito1 and Takayuki Sumida1

(1) Division of Clinical Immunology, Major of Advanced Biomedical Applications, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan
Received:

20 January 2006

Accepted:

04 April 2006

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Abstract

Antibodies against prothrombin are detected by enzyme immunoassays (EIA) in sera of patients with antiphospholipid syndrome (APS). However, there are two methods for antiprothrombin EIA; one that uses high binding plates (aPT-A), and another that utilizes phosphatidylserine bound plates (aPS/PT). We aimed to evaluate and compare aPT-A and aPS/PT in a clinical setting. We performed EIA for anti-PT, anti-PS/PT, IgG, and IgM anticardiolipin antibodies (aCL), and IgG β2-glycoprotein I-dependent aCL (aβ2GPI/CL) with serum samples from 139 systemic lupus erythematosus (SLE) patients (16 with history of at least one thrombotic episode) and 148 controls. We observed that: (1) although titers of anti-PT and anti-PS/PT were significantly related with each other (P < 0.0001, ρ = 0.548), titer of anti-PT and anti-PS/PT differed greatly in some samples; (2) odds ratio and 95% confidence interval for each assay was 3.556 (1.221 10.355) for aPT-A, 4.591 (1.555 15.560) for aPS/PT, 4.204 (1.250 14.148) for IgG aCL, 1.809 (0.354 9.232) for IgM aCL, and 7.246 (2.391 21.966) for aβ2GPI/CL. We conclude that, while all EIA performed in this study except IgM aCL are of potential value in assessing the risk of thrombosis, aPS/PT and aβ2GPI/CL seemed to be highly valuable in clinical practice, and that autoantibodies detected by anti-PT and anti-PS/PT are not completely identical.

Key words

Antiphospholipid syndrome - Antiprothrombin antibody - Enzyme immunoassay - Systemic lupus erythematosus (SLE)