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The association between anticoagulation and adverse outcomes after a positive SARS-CoV-2 test among older outpatients: a population-based cohort study


Introduction — Anticoagulation may improve outcomes in patients with COVID-19 when started early in the course of illness.

Materials and Methods — This was a population-based cohort study using linked administrative datasets of outpatients aged ≥65 years old testing positive for SARS-CoV-2 between January 1 and December 31, 2020 in Ontario, Canada. The key exposure was anticoagulation with warfarin or direct oral anticoagulants before COVID-19 diagnosis. We calculated propensity scores and used matching weights (MWs) to reduce baseline differences between anticoagulated and non-anticoagulated patients. The primary outcome was a composite of death or hospitalization within 60 days of a positive SARS-CoV-2 test. We used the Kaplan-Meier method and cumulative incidence functions to estimate risk of the primary and component outcomes at 60 days.

Results — We studied 23,159 outpatients (mean age 78.5 years; 13,474 [58.2%] female), among whom 3200 (13.8%) deaths and 3183 (13.7%) hospitalizations occurred within 60 days of the SARS-CoV-2 test. After application of MWs, the 60-day risk of death or hospitalization was 29.2% (95% CI 27.4%–31.2%) for anticoagulated individuals and 32.1% (95% CI 30.7%–33.5%) without anticoagulation (absolute risk difference [ARD], −2.9%; p = 0.005). Anticoagulation was also associated with a lower risk of death: 18.6% (95% CI 17.0%–20.2%) with anticoagulation and 20.9% (95% CI 19.7%–22.2%) in non-anticoagulated patients (ARD -2.3%; p = 0.005).

Conclusions — Among outpatients aged ≥65 years, oral anticoagulation at the time of a positive SARS-CoV-2 test was associated with a lower risk of a composite of death or hospitalization within 60 days.



Abdel-Qadir H, Austin PC, Pang A, Udell JA, Geerts WH, McNaughton CD, Jackevicius CA, Kwong JC, Yeh C, Cox JL, Lee DS, Ko DT, Atzema CL. Thromb Res. 2022; 211:114-22. Epub 2021 Dec 12.

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