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3221 Thrombotic Events in COVID-19 Patients Undergoing Convalescent Plasma Therapy: A Systematic Review

Program: Oral and Poster Abstracts
Session: 331. Thrombosis: Poster III
Hematology Disease Topics & Pathways:
Biological, Therapies, Adverse Events, Transfusion, Clinical Practice (e.g. Guidelines, Health Outcomes and Services, and Survivorship, Value; etc.)
Monday, December 13, 2021, 6:00 PM-8:00 PM

Philip Yu1*, Faran Khalid, BSc2*, Allen Li, BHSc3*, Marissa Laureano, MD4 and Mark Crowther, MD5

1Faculty of Health Sciences, McMaster University, Hamilton, ON, Canada
2Michael G DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada
3School of Medicine, University of Ottawa, Ottawa, ON, Canada
4Department of Medicine, McMaster University, Hamilton, ON, Canada
5McMaster University and St Joseph's Hospital, Hamilton, ON, Canada


Convalescent plasma therapy (CPT) has been proposed as a mechanism of passive immunization against COVID-19. Current guidelines on the efficacy of its use is not well delineated with limited studies analyzing the risk of thromboembolic events during treatment. The goal of this systematic review and meta-analysis was to assess the risk of arterial and venous thromboembolisms from CPT in patients with COVID-19.


We conducted a comprehensive literature review of Ovid MEDLINE, Cochrane Central Registry of Controlled Trials (CENTRAL), and EMBASE from inception to June 2021. Title and abstract screening and full-text screening was done in duplicate by two independent reviewers. All randomized controlled trials and cohort studies that analyzed adult COVID-19 patients undergoing CPT were included for analysis. Editorials, conference abstracts, narrative reviews, case series, containing less than 100 patients were excluded. The primary outcome analyzed was the risk of thrombotic events in CPT + standard therapy vs standard therapy alone. Meta-analysis was done using a random-effects model using the Revman 5 software.


Of 1774 studies identified from our search, three randomized (n= 660 patients), and one non-randomized matched cohort study) (n = 96 patients) were included for analysis. The risk ratio for thrombotic events was 2.33, favoring the CPT group (95% CI, [0.70, 7.72], P = 0.17, I2 = 29%). Subgroup analyses showed that CPT + standard therapy was associated with a decreased risk of in-hospital mortality (RR = 0.70 [0.49, 0.98], P = 0.04, I2 = 0%). No significant difference in cardiovascular events (RR = 0.90 [0.67, 1.20], P = 0.48, I2 = 0%), hypertension (RR = 1.67 [0.56, 4.98], P = 0.35, I2 = 0%), and septic shock (RR = 0.97 [0.40, 2.35], P = 0.94, I2 = 41%) was found between CPT + standard therapy and standard therapy alone.


We found treatment of COVID-19 with standard therapy + CPT was not associated with an increase in the risk of thromboembolic events. CPT was associated with a decreased risk of in-hospital mortality but not of MACE, hypertension, or septic shock.

Disclosures: Crowther: Hemostasis reference laboratories: Honoraria; Bayer: Speakers Bureau; CSL Behring: Speakers Bureau; Precision Biologicals: Honoraria; Pfizer: Speakers Bureau; Syneos Health: Honoraria.

*signifies non-member of ASH