An increased risk of deep vein thrombosis, pulmonary embolism, and bleeding may exist for individuals with COVID-19, according to study results published in the British Medical Journal.

Previous conflicting reports concerning venous thromboembolism risk following COVID-19 led researchers to investigate the risk of deep vein thrombosis, pulmonary embolism, and bleeding following COVID-19. To accomplish this, they conducted a self-controlled case series and matched cohort study between February 2020 and May 2021 of 1,057,174 individuals in Sweden who tested positive for SARS-CoV-2 and matched for age, sex, and county of residence to 4,076,342 control individuals. Information on all patients and controls was gathered from Swedish national registries. Risk ratios and incident rate ratios were calculated using self-controlled case series and conditional Poisson regression.

Incident rate ratios showed significant increases for deep vein thrombosis 70 days following COVID-19, for pulmonary embolism 110 days following COVID-19, and for bleeding 60 days following COVID-19. The initial pandemic wave in Sweden showed higher rate ratios than subsequent waves, and patients with critical COVID-19 displayed the highest rate ratios. Statistical analysis was related to first incidents of COVID-19, while first or recurrent deep vein thrombosis, pulmonary embolism, or bleeding events were chosen for analysis.


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In the first month following COVID-19, incident rate ratios for deep vein thrombosis were 5.90 (95% CI, 5.12-6.80), pulmonary embolism 31.59 (95% CI, 27.99-35.63), and bleeding 2.48 (95% CI, 2.30-2.68). Risk ratios in the same time period for deep vein thrombosis were 4.98 (95% CI, 4.96-5.01), pulmonary embolism were 33.05 (95% CI, 32.8-33.3), and bleeding were 1.88 (95% CI, 1.71-2.07), all adjusted for confounders. The absolute risk for patients with COVID-19 for deep vein thrombosis was 0.039% (401 events), pulmonary embolism was 0.17% (1761 events), and bleeding was 0.101% (1002 events).

Incomplete or inaccurate data from national registries was a limitation of this study, as was possible under diagnosis of venous thromboembolism in patients with COVID-19. Registry data for patients with COVID-19 dated from 1987, while registry data for controls dated from 1997, possibly leading to incorrect classification of “first events” for controls, and no vaccine data was available and the vaccine may have attenuated the risk of adverse events.

The study authors wrote, “The findings of this study suggest that COVID-19 is a risk factor for deep vein thrombosis, pulmonary embolism, and bleeding.” They believe their study argues for thromboprophylaxis especially for those patients who present high risk. The study authors went on to say, “It remains to be established whether SARS-CoV-2 infection increases the risk of venous thromboembolism or bleeding more than it does for respiratory infections, such as influenza, but also whether the period of thromboprophylaxis after COVID-19 should be extended.”

Reference

Katsoularis I, Fonseca-Rodríguez O, Farrington P, et al. Risks of deep vein thrombosis, pulmonary embolism, and bleeding after COVID-19: Nationwide self-controlled cases series and matched cohort study. BMJ. Published online April 6, 2022. doi:10.1136/bmj-2021-069590