Background: Pulmonary embolism (PE) remains a major cause of cardiovascular morbidity and mortality. Classical risk factors explain only part of the interindividual variability in thrombotic risk. Non-O blood groups are associated with higher plasma levels of von Willebrand factor and factor VIII, suggesting a potential prothrombotic mechanism. This systematic review and limited meta-analysis examined the relationship between ABO blood group and PE risk. Methods: Following PRISMA 2020 guidelines, PubMed, Embase, and Web of Science were searched through August 2025 for observational studies reporting ABO blood group and objectively confirmed PE in adults. Eligible designs included cohort, case–control, and registry-based studies. Two reviewers independently extracted data and assessed risk of bias using the Newcastle–Ottawa Scale. Comparable effect estimates were pooled using a random-effects model (DerSimonian–Laird method, inverse-variance weighting). Results: Four studies met inclusion criteria, comprising more than 300,000 participants from North America, Europe, and Asia. All reported a higher incidence of PE among non-O compared with O blood groups. Pooled analysis of two large population-based cohorts yielded a summary relative risk of 1.36 (95% CI 1.20–1.54; I² = 2.6%), indicating a modest but consistent association. Data on recurrence, severity, and mortality were limited and heterogeneous. Conclusions: Non-O blood groups are associated with an approximately 30–40% higher risk of PE across diverse populations. While evidence is insufficient for causal inference, ABO phenotype represents a biologically plausible and readily available marker that may complement multifactorial models of thromboembolic risk.

The influence of COVID-19 infection on the association between ABO blood groups and early outcomes in patients with acute pulmonary embolism (PE) remains uncertain. We conducted a retrospective, single-center cohort study including adult patients admitted with a first episode of acute pulmonary embolism (PE). The interaction between ABO blood group (non-O vs. O) and COVID-19 status was evaluated using multivariable logistic regression models adjusted for PE severity assessed by the Pulmonary Embolism Severity Index (PESI). A total of 211 patients were included, of whom 95 (45.0%) were COVID-19-positive. Among COVID-19-positive patients, non-O blood groups were associated with significantly higher odds of invasive mechanical ventilation (IMV) compared with group O (adjusted odds ratio [aOR] 12.87, 95% CI 4.17–39.75), whereas no association was observed among COVID-19–negative patients (aOR 1.20, 95% CI 0.45–3.23). No interaction was identified for 24 h mortality (p = 0.721) or systemic thrombolysis (p = 0.306). Higher PESI class was independently associated with an increased risk of adverse outcomes. ABO blood group modified the association between COVID-19 infection and early respiratory outcomes in acute PE. These findings suggest a potential role of ABO-related differences in coagulation and endothelial biology in the clinical expression of COVID-associated PE and should be interpreted as hypothesis-generating.

Background. Non-O ABO blood groups are known to confer an increased risk of venous thromboembolism, primarily through higher circulating levels of von Willebrand factor and factor VIII. However, it remains unclear whether ABO type affects biochemical profiles at the time of presentation or alters the prognostic value of commonly used biomarkers in acute pulmonary embolism (PE). This study examined the relationship between ABO blood group, baseline biomarkers, and short-term clinical outcomes in patients with confirmed acute PE. Methods. We performed a retrospective cohort study of adults admitted with computed tomography pulmonary angiography-verified PE at a single tertiary center. Associations between biomarkers and clinical outcomes were assessed using logistic regression adjusted for age, sex, active cancer, chronic kidney disease, obesity, and ABO group. Interaction terms tested whether ABO type modified biomarker–outcome relationships. Results. Among 317 included patients (median age 69 years), in-hospital mortality was 11.0%; 29.6% experienced severe PE, 48.3% developed infection, and 11.7% developed sepsis. Baseline biomarker distributions were similar across ABO groups, and multivariable models showed no independent association between non-O type and biomarker levels. NT-proBNP, CRP, and procalcitonin predicted in-hospital mortality, while NT-proBNP, procalcitonin, and CK-MB predicted severe PE. CRP, procalcitonin, D-dimer, creatinine, and leukocyte count were associated with infectious and septic complications. ABO type did not meaningfully modify biomarker–outcome relationships, aside from one exploratory interaction for infection. Sensitivity analyses confirmed the robustness of these findings. Conclusions. ABO blood group did not influence baseline biomarker profiles or the prognostic performance of key biomarkers in acute PE. Early outcomes were instead driven by indicators of right ventricular strain, inflammation, and renal dysfunction.