Background: Acute pulmonary thromboembolism (PTE) is the most common manifestation of venous thromboembolism (VTE). Due to the physiological response of circulating leukocytes to stress, circulation neutrophils increase and lymphocytes decrease. Therefore, the neutrophil-to-lymphocyte ratio (NLR) and the platelet-to-lymphocyte ratio (PLR) can be important measures to assess the severity of systemic inflammation. We sought to study NLR and PLR and their relationships with the severity of VTE and mortality.
 
Methods: The study enrolled 331 patients with VTE from 2014 through 2018. Based on the complete blood count obtained from the peripheral blood samples of the patients on admission, NLR and PLR were calculated. The incidence of VTE with or without PTE, as well as its severity, was determined based on computed tomography angiography findings and the patients’ clinical status.
 
Results: A positive relationship was observed between PTE and NLR (P=0.01). There was a significant relationship between the NLR and PLR values and PTE based on computed tomography angiography findings (NLR: P=0.001, PLR: P=0.012), but no relationship was detected between the ratios and the patients’ PTE severity based on clinical status. A significant relationship was also observed between NLR and the main pulmonary artery and segmental involvement (P=0.009), while no such association was seen with PLR. Additionally, the results revealed a significant relationship between NLR and mortality (P=0.030).
 
Conclusions: Our results demonstrated a significant relationship between the NLR and PLR values and PTE severity based on computed tomography angiography results and also mortality in patients with PTE. (Iranian Heart Journal 2022; 23(1): 65-73)