Abstract
Introduction: Antiphospholipid (aPL) antibodies are commonly detected in patients with primary immune thrombocytopenic purpura (ITP) and whether the presence of these antibodies affect the prognosis of the disease is not known yet. Nevertheless, knowledge on the role of aPL in primary ITP would contribute to the management of the disease.
Aim: Our primary aim was to evaluate if aPL antibodies are associated with either persistence or chronic primary ITP. We also aimed to evaluate the association of aPL antibodies with platelet counts and any bleeding event during the follow-up.
Methods: This is a retrospective cohort study that took place in the Hematology Center of the University of Campinas. We collected data on patients with primary ITP diagnosed between January 2008 and January 2016. Lupus anticoagulant (LAC), IgG/IgM anticardiolipin and antibeta2glycoprotein1 (aB2GP1) assays were performed at diagnosis, and repeated within 12 weeks when positive. We compared the baseline characteristics of patients with and without aPL using chi-square test, when variables were categorical, or independent t-test when variables were continuous. We used logistic regression and linear regression to examine the association between aPL and binary and continuous outcomes respectively. Cox regression was used to evaluate the cumulative risk of bleeding. Analysis were adjusted for age and sex.
Results: One hundred ninety-six patients were included and the median follow up time was 41 months. Forty-nine patients (21%) were positive for aPL (29 LAC, 20 aB2GP-1, 25 anticardiolipin IgM ou IgG, and 4 triple-positive). Baseline characteristics were similar between groups. Positivity for aPL was not associated with the risk of either persistent (OR=1,5 95%CI= 0.8; 3.0) or chronic ITP (OR=1,2 95%CI= 0.6;2.4). Mean platelet counts at 3 months was 123 x 103 (SD 111 x 103) U/mL in aPL negative patients and 103 x 103 (SD 117 x 103) U/mL in aPL positive patients (mean difference -18 x103 [95%CI= -55 to 18 x103]). Mean platelet counts at 12 months was 127 x 103 U/mL in aPL negative patients and 117 x 103 U/mL in aPL positive patients (mean difference -10 x103 [95%CI= -50 to 29 x103]). aPL positivity was not associated with bleeding events (HR= 1.3 95%CI=0.9; 1.8).
Conclusion: Our results demonstrated that the presence of aPL does not influence the clinical course of primary ITP. This suggests that the investigation of aPL may not be useful for the management of primary ITP.
De Paula:Hematology and Transfusion Medicine Center, University of Campinas: Employment.
