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Abstract Number: 10

Autoantibodies Targeting Domain 1 Of Beta 2 Glycoprotein I As Promising Marker In The Diagnosis and Risk Stratification Of The Antiphospholipid Syndrome

Navid Zohoury1, Munther A. Khamashta2, Tatsuya Atsumi3, Jacek Musial4, Toshiyuki Watanabe5, Maria Papp6, Concepción González-Rodríguez7, Roger Albesa1, Gary L. Norman1, Pier-Luigi Meroni8 and Michael Mahler1, 1Research, INOVA Diagnostics, San Diego, CA, 2Lupus Research Unit, The Rayne Institute, St Thomas Hospital, Kings College London School of Medicine, London, United Kingdom, 3Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine, Sapporo, Japan, 4Depment of Medicine, Jagiellonian University Medical College, Krakow, Poland, 5Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine, Hokkaido, Japan, 6MHSCInstitute of Medicine, Department of Gastroenterology, University of Debrecen, Debrecen, Hungary, 7University Hospital Virgen Macarena, Sevilla, Spain, 8Int Medicine, University of Milan, Milano, Italy

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: Antiphospholipid antibodies, antiphospholipid syndrome, autoantibodies, autoimmune diseases and thrombosis

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Session Information

Session Title: Antiphospholipid Syndrome: Clinical Manifestations and New Biomarkers in Antiphospholipid Syndrome

Session Type: Abstract Submissions (ACR)

Background/Purpose:

Antiphospholipid Syndrome (APS) is characterized by the presence of antibodies to phospholipids (aPL) and to β2glycoprotein I (β2GPI) in patients with thrombosis or pregnancy morbidity. Several studies provided evidence that antibodies to Domain 1 of β2GPI (β2GPI-D1) represent a promising biomarker for the diagnosis and risk assessment of APS patients. Here we aimed to analyze the diagnostic potential of β2GPI-D1 antibodies and the value in risk stratification of APS patients using a large multi-centric cohort of patients.

Methods:

A total of 273 APS patients and 1096 controls (including healthy individuals, patients with infectious or autoimmune diseases) were tested for anti-β2GPI-D1 by QUANTA Flash CIA (INOVA). A reduced number of samples (n=622) were also tested on anti-β2GPI by QUANTA Flash CIA (INOVA). Clinical data including the history of thrombosis was known in 89 APS patients (58 had a history of thrombosis).

Results:

In the entire cohort, anti-β2GPI-D1 antibodies differentiated APS and controls with a sensitivity and specificity of 49.8% and 99.6%, respectively. The likelihood ratios were LR+ 136.5 and LR- 0.5. The prevalence of anti-β2GPI antibodies was higher in primary than in secondary APS and reach significance for anti-β2GPI-D1 (p=0.0029), but not for anti-β2GPI antibodies (p=0.06). When compared with the anti-β2GPI assay, both assays showed good qualitative (79.8%, 95% CI 69.1-86.5; kappa=0.60, 95% CI 0.44-0.76) and quantitative agreements (spearman`s rho=0.81, 95% CI 0.73-0.87) as well as similar discrimination between APS patients and controls as shown by ROC analysis. In the smaller sub-cohort (n=622), sensitivity/specificity were 50.2%/99.2% (β2GPI-D1) and 72.8%/87.3% (β2GPI), respectively.

Assay

Cut-off

Sensitivity (95% Confidence interval)

Specificity (95% Confidence interval)

LR+/LR- at cut-off

β2GPI

20 CU

72.8 (66.6-78.4)

83.7 (79.7-87.3)

4.5/0.33

β2GPI-D1

20 CU

50.2 (43.6-56.8)

99.2 (97.8-99.8)

64.8/0.50

β2GPI

50.9 CU

62.1 (55.6-68.4)

96.9 (94.6-98.4)

20.0/0.39

β2GPI-D1

7.3 CU

60.0 (53.4-66.3)

96.9 (94.6-98.4)

19.4/0.41

β2GPI

91.1 CU

57.4 (50.9-63.9)

99.0 (97.4-99.7)

55.6/0.43

β2GPI-D1

11.1 CU

56.2 (49.6-62.6)

99.0 (97.4-99.7)

54.3/0.44

When APS patients were stratified according to the history of thrombosis, anti-β2GPI-D1 and anti-β2GPI antibodies showed sensitivities/specificities of 37.9%/93.5% and 60.3%/67.7% respectively. At high specificity (96.8%), the sensitivity for thrombosis was significantly higher for β2GPI-D1 than for β2GPI (22.4% vs. 12.1%; p<0.05).

Assay

Cut-off

Sensitivity (95% Confidence interval)

Specificity (95% Confidence interval)

LR+/LR- at cut-off

β2GPI

20 CU

60.3 (46.6-73.0)

67.7 (48.6-83.3)

1.87/0.59

β2GPI-D1

20 CU

37.9 (25.5-51.6)

93.5 (78.6-99.2)

5.88/0.66

β2GPI

4868 CU

12.1 (5.0-23.3)

96.8 (83.3-99.9)

3.74/0.91

β2GPI-D1

286.9 CU

22.4 (12.5-35.3)

96.8 (83.3-99.9)

6.95/0.80

Conclusion:

Anti-β2GPI-D1 and anti-β2GPI antibodies show similar performance characteristics in differentiation of APS patients and controls. The correlation with history of thrombosis appears to be stronger for anti-β2GPI-D1 compared to anti-β2GPI-antibodies. Therefore, anti-β2GPI-D1 antibodies are a promising biomarker to aid in the diagnosis and risk assessment of APS patients, but further studies are needed to verify those preliminary findings.


Disclosure:

N. Zohoury,

Inova Diagnostics, Inc.,

3;

M. A. Khamashta,

Inova Diagnostics, Inc.,

5;

T. Atsumi,
None;

J. Musial,
None;

T. Watanabe,
None;

M. Papp,
None;

C. González-Rodríguez,
None;

R. Albesa,

Inova Diagnostics, Inc.,

3;

G. L. Norman,

Inova Diagnostics, Inc.,

3;

P. L. Meroni,

Inova Diagnostics, Inc.,

5;

M. Mahler,

Inova Diagnostics, Inc.,

3.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/autoantibodies-targeting-domain-1-of-beta-2-glycoprotein-i-as-promising-marker-in-the-diagnosis-and-risk-stratification-of-the-antiphospholipid-syndrome/

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