Association between pre-admission anticoagulation and in-hospital death, venous thromboembolism, and major bleeding among hospitalized COVID-19 patients in Japan.

Purpose: The coagulation activation leads to thrombotic complications such as venous thromboembolism (VTE) in patients with coronavirus disease-2019 (COVID-19). Prophylactic anticoagulation therapy has been recommended for hospitalized COVID-19 patients in clinical guidelines. This retrospective cohort study aimed to examine the association between pre-admission anticoagulation treatment and three outcomes: in-hospital death, VTE, and major bleeding among hospitalized COVID-19 patients in Japan.

Methods: Using a large-scale claims database built by the Medical Data Vision Co. in Japan, we identified patients hospitalized for COVID-19 who had outpatient prescription data at least once within 3 months before being hospitalized. Exposure was set as pre-admission anticoagulation treatment (direct oral anticoagulant or vitamin K antagonist), and outcomes were in-hospital death, VTE, and major bleeding. We conducted multivariable logistic regression analyses, adjusting for a single summarized score (a propensity score of receiving pre-admission anticoagulation) for VTE and major bleeding, due to the small number of outcomes.

Results: Among the 2612 analytic patients, 179 (6.9%) had pre-admission anticoagulation. Crude incidence proportions were 13.4% versus 8.5% for in-hospital death, 0.56% versus 0.58% for VTE, and 2.2% versus 1.1% for major bleeding among patients with and without pre-admission anticoagulation, respectively. Adjusted odds ratios (95% confidence intervals) were 1.25 (0.75-2.08) for in-hospital death, 0.21 (0.02-1.97) for VTE, and 2.63 (0.80-8.65) for major bleeding. Several sensitivity analyses did not change the results.

Conclusions: We found no evidence that pre-admission anticoagulation treatment was associated with in-hospital death. However, a larger sample size may be needed to conclude its effect on VTE and major bleeding.