Comparing follow-up of patients with vitamin K antagonists in a health center: pre- and post- COVID-19 pandemic

Introduction and objectives: During the COVID-19 pandemic, the follow-up of patients treated with vitamin K antagonists (VKAs) may have been affected. This study aims to compare how these patients were monitored preand post-COVID-19 pandemic and understand the impact of non-face-to-face appointments on their follow-up. Methods: We conducted a retrospective cohort study in a Portuguese Health Center. The study included patients treated with VKAs and followed at the Health Center for international normalized ratio (INR) monitoring between March 2019 and March 2021. Data collected: sex, age, type of VKA; INR; date of INR assessment, type of appointment (face-to-face or phone/e-mail). Rosendaal’s method was used to calculate pre-COVID-19 and post-COVID-19 time in therapeutic range (TTR). Good TTR control was defined if values ≥ 70%. Results: 44 patients were included. The mean TTR in the pre-COVID-19 period was 64.55% (95% CI: 58.10 - 71.00%). The post-COVID-19 mean was slightly higher (+ 2.26%), 66.81% (95% CI: 59.66 - 73.97%), but the difference was not statistically significant (p = 0.576). The use of non-face-to-face appointments did not contribute to worsening post-pandemic TTR, showing no lower follow-up than during pre-pandemic period in which all contacts were face-to-face [CI (95%) -0.397 - 0.196 for a reference range -0.489 - 0.693]. Conclusions: The TTR value in both periods was similar and lower than the value defined for effective hypocoagulation. The use of non-face-to-face consultation in the post-COVID-19 period does not seem to have influenced the quality of hypocoagulation.