Despite the frequent occurrence of thrombocytopenia in patients with acute pulmonary thromboembolism (PTE), there is great uncertainty regarding the effect of baseline thrombocytopenia on clinical outcomes in patients with PTE in the anticoagulation era. Balancing bleeding and thrombosis risks during periods of thrombocytopenia faces a complex challenge. However, there is a scarcity of current evidence and the optimal anticoagulation management strategies in this population is controversial. Baseline characteristics, management pattern and clinical outcome of PTE and thrombocytopenia needs to be reported.

To explore how baseline thrombocytopenia influences the incidence of venous thromboembolism (VTE) recurrences, bleeding events and all-cause mortality. 

Patients with acute PTE enrolled between 2016 to 2021 were selected from a large prospective nationwide cohort in China. This is a post-hoc analysis and patients with available values of platelet counts were included. Individuals from the thrombocytopenia cohort were matched with patients (1:4 ratio) from the control cohort using propensity score matching based on age and sex. Data on demographic parameters, comorbidities, clinical presentation, laboratory tests, anticoagulation initiation and 2-year follow-up outcomes were collected and analyzed. The thrombocytopenia cohort was defined as platelet counts ≤100 000/uL on admission. The primary outcomes including 2-year cumulative incidence of bleeding and recurrent VTE, and secondary outcome was all-cause mortality. A multivariable analysis was conducted to explore the association between platelet levels and outcomes using a piecewise Cox hazard model. Kaplan-Meier curves and log-rank test were performed to show the association between platelet and all-cause mortality, recurrent thrombosis or bleeding.

Among 1880 patients with acute PTE were included in the study after matching: 376 Patients with thrombocytopenia at baseline and 1504 Patients in the control cohort. The median age was 73 years (IQR: 61-81 years) and males accounted for 58.5%. Platelet levels revealed a significant differences on heart failure, liver cirrhosis, connective tissue disease, hematopathy, BMI, blood pressure, heart rate, hemoglobin, total bilirubin, urea nitrogen and creatinine. Low molecular weight heparin for acute PTE were also similar between the groups (79.6% vs. 79.1%). Among patients with PTE and thrombocytopenia, 7.51% patients did not use anticoagulant drugs. The 30-day and 90-day all-cause mortality rates from PTE were 12.2%  and 18.0% for thrombocytopenia, 4.2% and 7.5% for normal platelet counts. During a follow-up of 2-year, the incidence of  recurrent VTE (0.41% vs. 0.28%) and bleeding (5.73% vs. 5.25%) were no significant differences between the groups. The multivariate Cox analysis showed that thrombocytopenia was independently associated with an increased risk of all-cause mortality (hazard ratio=2.48 ; 95% confidence interval=1.23-5.0; Log-rank p=0.023). By contrast, there were no significant association for bleeding and recurrent VTE.

The platelet counts, is amenable to reliable assay in most medical centers. These findings suggest that in patients with acute PTE, thrombocytopenia at baseline was associated with increased risk of long-term death. For patients with acute PTE, Platelet could emerge as the biomarker of choice for risk stratification and may also inform treatment strategies.