High risk of thromboembolic events in adult with primary immune thrombocytopenia: results from a prospective cohort study

Introduction Patients with primary immune thrombocytopenia (ITP) have an increased risk of bleeding but paradoxically also an increased thromboembolic risk

Method Between March 2017 and July 2023, 160 patients with primary ITP were enrolled in the Vienna ITP Biobank, a prospective dual-center cohort study (Medical University of Vienna; Hanusch Hospital, EC 1843/2016). Descriptive analysis was performed and the associations between clinical risk factors and prospective thrombotic events (TE) were identified using univariate and multivariate logistic regression analyses.

Results 160 ITP patients were followed for median duration of 35 months (inter-quartile range (IQR): 26-52). Of them 17 (10.6%) patients experienced a TE after a median of 32 months (IQR: 12-53). These events consisted of 6 ATE (35%), including 3 acute myocardial infarctions, 1 cerebral vascular events (stroke or transient ischemic attack) and 2 peripheral artery thrombosis and 11 (64.7%) VTE, inlcuding 4 superficial vein thromboses, 4 deep vein thromboses and 3 cases of isolated pulmonary embolism. The cumulative 1- and 5- year incidence of TE accounting for competing mortality were 4.4% and 9.4%. Four (23.5%) of the patients with thrombosis died during the follow-up period. The cause of death was unclear for three patients, while one patient died from pulmonary embolism. Cardiovascular risk factors were more prevalent in ATE patients ([Fig. 1]). At time of thrombosis the median (IQR) platelet count in patients was 197 (66-218) and 11 (64.7%) patients received ITP-speciffic treatment, of whom 9 (81.8%) received thrombopoeitin-receptor agonists. In univariate regression analysis, age over 60 years (OR 6.8 95% CI 1.4-11.1, p=0.009), the presence of antiphospholipid antibodies (APLA) (OR 3.5 95%CI 1.0-11.4, p=0.035), particularly lupus anticoagulant positivity (OR 2.80; 95% CI 1.8-9.8, p=0.022) and anti-cardiolipin antibody positivity (OR 4.7 95% CI 1.2-25.1, p=0.030), and previous thrombosis (OR 10.2; 95% CI 3.4-30.5, p=0.001), were significantly associated with a higher risk of arterial and venous TE among ITP patients ([Fig. 2]). After conducting multivariate logistic regression analysis, age≥60 and previous thrombosis were found to be the only independent significant risk factors for developing TE (OR 3.8 95% CI 1.34-43.28, p=0.044; OR 13.2 95% CI 3.1-45.2 p=0.001).

Fig. 1 Univariate and multivariate Logistic regression Analysis. IQR, interquartile range; LA, lupus anticoagulant , aCL Ab, anti-cardiolipin antibodies; ab2GPI Ab, anti-b2 glycoprotein I antibodies; TPO-RAs, thrombopoietin-receptor agonist statistically significant . p-value<0.05

Fig. 2 Baseline characteristics at time of study inclusion of patients with ITP; interquartile range; BMI, body mass index; LA, lupus anticoagulant, aCL Ab, anti-cardiolipin antibodies; ab2GPI Ab, anti-b2 glycoprotein I antibodies; TPO-RAs, thrombopoietin-receptor agonist*statistically significant . p-value<0.05

Conclusion We observed high rates of arterial and venous TE in our patients. Previous thrombosis, APLA positivity, age, confirmed as thrombosis risk factors in our study. Although, ITP patients commonly present with cardiovascular risk factors, our study did not find that these factors affected thrombotic ris. Close monitoring and tailored treatment strategies should be applied to minimize the risk of thrombotic events in ITP patients at risk.

Conflict of Interest

The biobank from which this data derives is supported by Novartis, Swedish Orphan Biovitrum (SOBI), MedMedia Verlag und Mediaservice GmbH and AMGEN GmbH

Publication History

Article published online:
26 February 2024