Abstract Number: OC 06.1
Meeting: ISTH 2022 Congress
Background: Data on the effect of rituximab on antiphospholipid antibody (APLA) titers in patients with antiphospholipid syndrome (APS) are limited.
Aims: Determine the effect of rituximab on APLA titers in APS patients within 12 months of treatment.
Methods: Patients with APS, age ≥ 18, within the University of North Carolina Health Care Systems identified via electronic medical record review from 1994-2020 using: keyword rituximab, ICD codes for arterial/venous thromboses, APS/CAPS, and CPT codes for lupus anticoagulant (LA), anticardiolipin (aCL) IgM/IgG, and anti-β2-glycoprotein I (aβ2GPI) IgM/IgG. Definitions used: LA positive if DRVTT ratio ≥ 1.20 and/or LA-aPTT HPN difference > 8 seconds, aCL/aβ2GPI: low < 40, medium 40-100, and high >100. ‘Time zero’ includes the start and stop dates of the first treatment course with rituximab, with negative and positive times corresponding to the before the start date or after the stop date, respectively. Lab observations 12 months before and after time zero were collected but censored after the start of the second treatment, if applicable. Titer changes are described.
Results: 9/37 patients (1 catastrophic APS) were eligible for analysis (figure 1). Changes in aCL/aβ2GPI titers for each patient are presented in figure 2.
– LA: 6/9 were positive before rituximab; all remained positive after treatment.
– aCL IgG (6/9): 5/6 medium, 1/6 high. None became negative: 3/6 remained unchanged; 1/6 medium to high, 1/6 medium to low, and 1/6 high to medium.
– aCL IgM (3/9): all medium titers: 2/3 became negative, 1/3 unchanged.
– aβ2GPI IgG (6/9): 3/6 low, 1/6 medium, 2/6 high. After treatment 3/6 unchanged, 2/6 low to medium, 1/6 medium to high, and 1/6 negative to medium.
– aβ2GPI IgM (2/9): remained unchanged.
– 1/9 had a recurrent thrombotic event within 1 year of treatment.
Conclusion(s): Rituximab did not have a meaningful overall effect on the APLA titers.
To cite this abstract in AMA style:Youkhana K, Heiling H, Deal A, Moll S. The effect of rituximab on antiphospholipid antibody titers in patients with Antiphospholipid Syndrome. [abstract]. https://abstracts.isth.org/abstract/the-effect-of-rituximab-on-antiphospholipid-antibody-titers-in-patients-with-antiphospholipid-syndrome/. Accessed October 2, 2023.
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