Abstract
Background/Objectives: The interplay between asthma and COVID-19 raises critical clinical questions, particularly regarding the risk of hematological complications in patients affected by both conditions. While COVID-19 is known to cause coagulopathy and thromboembolic events, it remains unclear whether asthma independently influences these risks. This systematic review aimed to synthesize existing evidence on hematological abnormalities-including D-dimer elevation, thrombocytopenia, and venous thromboembolism (VTE)-in asthmatic patients with confirmed SARS-CoV-2 infection. Methods: A systematic search was conducted in PubMed and Web of Science databases for studies published between January 2020 and May 2025. Inclusion criteria were studies reporting hematologic outcomes in asthmatic patients with COVID-19. After duplicate removal, 139 unique articles were screened, with 40 studies meeting inclusion criteria. These included observational cohorts, retrospective analyses, and clinical investigations. Data were synthesized in a systematic review with qualitative synthesis due to heterogeneity in design and reporting. Results: The review identified variable patterns of D-dimer elevation and thrombotic events among asthmatic COVID-19 patients. Some studies reported a higher incidence of ICU admission, elevated inflammatory and coagulation markers, and increased thromboembolic risk in asthmatic individuals-particularly those with poor disease control or non-allergic phenotypes. However, findings were inconsistent and often limited by the absence of asthma stratification, standardized outcome measures, and prospective designs. Conclusions: Current evidence does not support a definitive link between asthma and increased thrombotic risk in COVID-19. Further research with prospective, phenotype-stratified methodologies and harmonized hematologic endpoints is needed to clarify whether asthma modifies the hematologic trajectory of SARS-CoV-2 infection.