Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Evaluation of Non-Criteria Antiphospholipid (aPL) Assays at a Wet Workshop during the 13th International Congress on Antiphospholipid Antibodies.

Albesa1,  Roger, Nelson1,  Victoria, Shums1,  Zakera, Norman1,  Gary, Gu2,  X.-X., Rand2,  Jacob, Binder1,  Walter

INOVA Diagnostics, San Diego, CA
Montefiore, Albert Einstein School of Medicine, New York, NY
Univ of TX Med Branch, Galveston, Galveston, TX
Utretch Medical Center, Utrecht, The Netherlands

Background:

Recently new assays for the detection of Antiphospholipid antibodies (aPL) have been developed. These include immunoassays that detect antibodies directed to domain I (DI) of b2glycoprotein, that has been shown to be detect "thrombosis-related" anti-b2glycoprotein I (ab2GPI) antibodies and a new clotting/mechanistic test named the Annexin A5 resistance assay (A5R), that measures the ability of aPL antibodies to reduce the anticoagulant activity of A5 in vitro. Recent studies have shown a good correlation between aPL antibodies that recognize domain I of b2GPI and the reduction of the A5 anticoagulant activity.

Objective:

to evaluate the performance of two different ELISAs for the detection of DI (one in-house method and one commercial kit) and the A5R test in a wet workshop at the 13th International Congress on Antiphospholipid Antibodies in Galveston, TX (April 13th, 2010).

Methods:

An in-house method developed by B de Laat and colleagues that utilizes hydrophobic microtiter plates coated with recombinant domain I and a commercial kit (INOVA) were evaluated for the detection of anti-DI antibodies. Samples were also evaluated simultaneously in an IgG ab2GPI (INOVA) for comparison purposes. Aliquots of 26 APS patients and 21 controls (14 from healthy individuals and 7 from patients with infectious diseases) were distributed to the participants/groups. For the two-step A5R assay, procedure was carried out as published (Blood 2004; 104:2783–2790). Five plasmas from APS patients and five controls were tested prior to the workshop and at the workshop. In addition, normal plasmas were "spiked" with dilutions of various aPL monoclonal antibodies (MoAbs) IgG and IgM: a) HCAL and EY2C9 [Center for Diseases Control (CDC)]; b) AbyD05045 and AbyD03892 (Phadia); c) "Sapporo" (INOVA). The workshop was open to all congress attendees who registered for this event.

Results:

18 out of the 26 APS samples were positive in the IgG ab2GPI (INOVA) ELISA. Fourteen and 10 out of the 18 APS samples that were positive in the IgG ab2GPI, were positive in the DI ELISA (INOVA) and in-house respectively. This discrepancy is likely due to the fact that the in-house method is not calibrated for serum samples. All the samples that were positive in the DI ELISA (either in-house or INOVA kit) had evidence of thrombosis associated with aPL antibodes. All the APS plasmas as well as the IgM and IgA MoAbs (Phadia, INOVA and CDC) as well as the IgG INOVA MoAb reduced significantly the A5 anticoagulant activity. All negative plasmas were negative in the A5R.

Conclusions:

In this workshop, the A5R showed to be a sensitive and specific new mechanistic assay for aPL antibodies. Samples tested in the DI assays, which were tested single-blinded, appear to correctly identify a subset of "pathogenic" ab2GPI antibodies. Both assays appear to be promising assays for detecting patients at risk for thrombosis.

To cite this abstract, please use the following information:
Albesa, Roger, Nelson, Victoria, Shums, Zakera, Norman, Gary, Gu, X.-X., Rand, Jacob, et al; Evaluation of Non-Criteria Antiphospholipid (aPL) Assays at a Wet Workshop during the 13th International Congress on Antiphospholipid Antibodies. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2250
DOI: 10.1002/art.30013

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