Summary of the 9th meeting of the European Forum on Antiphospholipid Antibodies

Measuring IgA Anti-β2-Glycoprotein I and IgG/IgA Anti-Domain I Antibodies Adds Value to Current Serological Assays for the Antiphospholipid Syndrome

Introduction

Currently available clinical assays to detect antiphospholipid antibodies (aPL) test for IgG and IgM antibodies to cardiolipin (aCL) and β₂-glycoprotein I (aβ₂GPI). It has been suggested that testing for IgA aPL and for antibodies to Domain I (DI), which carries the key antigenic epitopes of β₂GPI, could add value to these current tests. We performed an observational, multicenter cohort study to evaluate the utility of IgG, IgM and IgA assays to each of CL, β₂GPI and DI in APS.

Methods

Serum from 230 patients with APS (n = 111), SLE but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA aCL, aβ₂GPI and aDI activity. Patients with APS were further classified into thrombotic or obstetric APS. Logistic regression and receiver operator characteristic analyses were employed to compare results from the nine different assays.

Results

All assays displayed good specificity for APS; IgG aCL and IgG aβ₂GPI assays however, had the highest sensitivity. Testing positive for IgA aβ₂GPI resulted in a higher hazard ratio for APS compared to IgM aβ₂GPI. Positive IgG, IgM or IgA aDI were all associated with APS, and in subjects positive for aCL and/or aβ₂GPI, the presence of aDI raised the hazard ratio for APS by 3–5 fold. IgG aCL, aβ₂GPI, aDI and IgA aDI were associated with thrombotic but not obstetric complications in patients with APS.

Conclusion

Measuring IgG aDI and IgA aβ₂GPI and aDI may be useful in the management of patients with APS, particularly thrombotic APS.

Development and initial validation of a damage index (DIAPS) in patients with thrombotic antiphospholipid syndrome (APS)

INTRODUCTION

In antiphospholipid syndrome (APS), certain principal manifestations are associated with a worse prognosis and organ damage.

OBJECTIVE

The objective of this paper is to describe the development and initial content, criterion and construct validity of a disease-specific cumulative damage index in patients with thrombotic APS (DIAPS).

METHODS

Through expert panel agreement, 47 items were considered to reflect damage in APS. This preliminary version of the DIAPS was submitted to four local and international clinical and research experts in APS who ranked each item according to severity. A Delphi exercise resulted in a final 37 item instrument. In the second phase, a cross-sectional study was conducted applying the DIAPS in patients included in a multicenter electronic registry of patients with APS. Quality of life related to health status was evaluated with the EuroQol for construct validation. An α Cronbach and correlation with the EuroQol scale were calculated with SPSS 20.0 (p < 0.05).

RESULTS

We evaluated the DIAPS in 156 patients, 77% female, with a mean age at diagnosis 34.7 ± 5.5 years. A total of 69% had primary APS. Common comorbidities included obesity, depression and dyslipidemia. The most frequent manifestations resulting in sequelae were deep venous thrombosis and ischemic stroke. Blindness, retinal occlusive vessel disease, myocardial infarction, cardiac valve requiring replacement, mesenteric thrombosis, and renal insufficiency also occurred. Homogeneity: α Cronbach 0.619. DIAPS items correlated with EuroQol domains with the exception of pulmonary, renal, gastrointestinal, and endocrine systems.

CONCLUSION

This study demonstrates content, criterion and construct validity of a new physician-reported instrument to assess the DIAPS. In addition, the DIAPS correlated with the EuroQol.