New studies assess effects of anticoagulation during, after COVID-19

Two new studies looked at anticoagulant therapy in patients with COVID-19.

One study, published by the Journal of Hospital Medicine on Nov. 8, retrospectively assessed the effects of standard prophylactic, intermediate, or full-dose anticoagulation in hospitalized patients. Researchers from a California health system included 22,054 inpatients with COVID-19 and respiratory impairment: 17,130 were analyzed based on the highest dosing of anticoagulation they received on the day of admission, and 4,924 were analyzed based on anticoagulation received within 24 hours of experiencing respiratory deterioration.

After adjustment by propensity score, the study found no differences in the rate of in-hospital death by anticoagulation strategy. Compared to standard prophylaxis, mortality was the same with intermediate (odds ratio [OR], 1.00 [95% CI, 0.89 to 1.12]) or full anticoagulation (OR, 1.00 [95% CI, 0.85 to 1.17]) on the day of admission, as well as on the day of deterioration (ORs, 1.22 [95% CI, 0.82 to 1.82] and 1.50 [95% CI, 0.90 to 2.51], respectively). Bleeding complications occurred in 2.2% of patients on standard prophylaxis, 2.4% on intermediate-dose anticoagulation, and 6.9% on full anticoagulation.

“The lack of observed benefit in the real-world settings of our study does not support the use of full anticoagulation in general ward patients with COVID-19, although our null findings can be explained alternatively by residual confounding or the play of chance,” said the study authors, who noted that patients receiving full anticoagulation could be sicker in ways that were not adjusted for. Previous studies on this question have had mixed results, said the authors, who called for additional trials and observational studies.

The other study, published as a research letter by JAMA Internal Medicine on Nov. 7, looked at duration of anticoagulation after a COVID-19-associated venous thromboembolism (VTE). The international study assessed patients who developed VTE within 30 days of confirmed COVID-19 infection and discontinued anticoagulation after at least three months of therapy. After exclusion for various factors, including upper-limb deep venous thrombosis (DVT), 431 patients were included in the study (mean age, 61.6 years; 60.3% men). Their median duration of anticoagulation was 4.6 months, and over a median follow-up of 5.8 months after discontinuation, 11 patients (2.6% [95% CI, 1.3% to 4.5%]) had recurrent VTE (six had DVT, three had pulmonary embolisms, and two had both). By 30 days, one patient had had both and one had a DVT.

The study authors calculated that the rate of recurrent VTE was 4.8 (95% CI, 2.4 to 8.6) per 100 patient-years, and that although the overall fatality rate in the study was 2.5%, the case-fatality rate of the VTE recurrences was 0%. They observed that the recurrence rate after discontinuation “was similar to that in patients with VTE associated with a transient nonsurgical factor (5.8% [95% CI, 3.2%-8.3%] per patient-year) and may be in line with the inflammatory response and acute illness in the context of COVID-19 improving over time.” Limitations of the study include its wide confidence intervals and that outcomes were ascertained by local clinicians without central validation, but the results support providing a limited course of anticoagulation to patients with COVID-19-associated VTE, the authors said.