To the Editor:
We thank The Journal for this opportunity to restate some of the findings in our report1.
One of our conclusions is that antiphosphatidylserine/prothrombin (aPS/PT) is associated with thrombosis in systemic lupus erythematosus (SLE), agreeing with the data published by Bertolaccini, et al2. We completely agree that aPS/PT should be considered as an additional test for antiphospholipid syndrome (APS) and should not be considered just a replacement for lupus anticoagulant (LAC). While most, but not all, aPS/PT-positive specimens are LAC-positive, not all LAC-positive specimens are aPS/PT-positive. Although the validity of LAC testing in anticoagulated patients might be debatable, our suggestion that aPS/PT IgG/IgM tests “might serve as a useful alternative to lupus anticoagulant” in these situations is reasonable.
We did not focus on comparing LAC-positive versus LAC-negative patients. Our table data1 compared thrombosis versus no thrombosis, stroke versus no stroke, etc. Our tables were not univariate analyses, but as stated in the footnote for each table, were adjusted for age, sex, and ethnicity. Additional analysis, adjusting for hypertension and hyperlipidemia, did not result in different conclusions.
Our focus was on 2 “novel” assays, aPS/PT and IgA antiphospholipid assays. Our work on anti-β2-GPI and thrombosis has been published previously3, and therefore was not the focus of the report.
The assays (aPS/PT and IgA) are not affected by anticoagulation. The Russell’s viper venom time test (RVVT) is, in our center, prolonged in anticoagulated patients. The RVVT confirmatory test may be valid (but can still be falsely positive in those with supratherapeutic international normalized ratios). We believe that alternatives to clotting assays are needed in the evaluation for antiphospholipid status.
REFERENCES
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