Clinical Accuracy for Diagnosis of Antiphospholipid Syndrome in Systemic Lupus Erythematosus: Evaluation of 23 Possible Combinations of Antiphospholipid Antibody Specificities

Savino Sciascia¹, Veronica Murru¹, Giovanni Sanna², Dario Roccatello³, Munther A. Khamashta⁴ and Maria Laura Bertolaccini¹, ¹Lupus Research Unit, The Rayne Institute, Kings College London School of Medicine, London, United Kingdom, ²Louise Coote Lupus Unit, St. Thomas' Hospital, London, United Kingdom, ³Department of Rare, Immunologic, Hematologic and Immunohematologic Diseases, Centro di Immunopatologia e Documentazione su Malattie rare, Torino, Italy, ⁴Lupus Research Unit, The Rayne Institute, St Thomas Hospital, Kings College London School of Medicine, London, United Kingdom

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: antiphospholipid syndrome, pregnancy, systemic lupus erythematosus (SLE) and thrombosis

Session Information

Title: Antiphospholipid Syndrome

Session Type: Abstract Submissions (ACR)

Background/Purpose: The clinical accuracy of testing for antiphospholipid antibody (aPL) both, as individual tests and/or in combination, is still being investigated. We aimed to identify a panel of tests that may provide the best accuracy for diagnosing the antiphospholipid syndrome (APS) in a wide cohort of patients with Systemic Lupus Erythematosus

Methods:

This study included 230 patients (218 women, mean age 42.7±11.9 years, mean disease duration 12.2±8.7years), all fulfilling the 1982 criteria for Systemic Lupus Erythematosus . Lupus anticoagulant (LA), anti-cardiolipin (aCL), anti-β₂glycoprotein I (anti-b2GPI), solid phase anti-prothrombin (aPT), anti-phosphatidylserine/prothrombin (aPS/PT), and anti-phosphatidylethanolamine (aPE) antibodies were tested in all. Sensitivity, specificity and predictive values were calculated. The diagnostic accuracy for each combination of tests was assessed by ROC and their area under the curve analysis (AUC) as well as by the Youden’s index (YI).

Results: Testing for 6 aPL derived in 23 possible combinations of results. Among them, LA+ anti-β₂GPI+aPS/PT had the best diagnostic accuracy for APS as a whole, and individually for both thrombosis and pregnancy loss (AUC 0.712, OR3.73 [95% CI 1.82-5.38], p=0.0001, YI= 0.32; AUC 0.709, OR3.75 [95% CI 2.13-6.62], p=0.0001, YI=0.37 and AUC 0.677, OR4.82 [95%CI 2.17-10.72], p=0.0007, YI= 0.38; respectively) and the best specificity when compared to all the other obtainable combination of tests. Triple positivity for LA+anti-β₂GPI+aPS/PT was more strongly associated with clinical events (thrombosis and/or Pregnacy Loss) than double or single positivity (OR23.2 [95%CI 2.57-46.2] vs. OR7.3 [95%CI 2.21-25.97], OR5.7 [95%CI 2.12-17.01] or OR3.11 [95%CI 1.56-7.8] for single positivity for LA, aPS/PT and anti-β₂GPI, respectively).

Conclusion:

Combining LA, anti-β₂GPI and aPS/PT improves the diagnostic power and helps in stratifying the risk for each patient, according to their aPL profile.

Disclosure:

S. Sciascia,
None;

V. Murru,
None;

G. Sanna,
None;

D. Roccatello,
None;

M. A. Khamashta,
None;

M. L. Bertolaccini,
None.

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