Monitoring anti-Xa levels in elderly medical patients undergoing thromboprophylaxis: A prospective cohort study

Given the rising incidence of venous thromboembolism (VTE) and insufficient thromboprophylaxis dosing evidence in certain patients, the precise monitoring of anti-Xa (aFXa) levels is crucial. The aim of this study is to investigate the achievement of prophylactic aFXa levels in medical inpatients who were receiving parenteral anticoagulant and to evaluate the impact of various factors on aFXa levels.

This is a single-center observational cohort study conducted on patients admitted to the Department of Internal Medicine at the University Hospital of Heraklion, Greece, from March to August 2023. These individuals received low-molecular-weight heparins thromboprophylaxis owing to an increased risk of VTE. Data regarding demographics, past medical history, and somatometric and laboratory findings were recorded. The established range for peak prophylactic aFXa levels was defined as 0.2-0.5 IU/mL.

In this study, we enrolled 150 individuals [91 (60.7%) women] with a mean age of 80.0 ± 14.1 years. Sixty-two (41.4%) patients exhibited non-prophylactic peak aFXa levels. Supratherapeutic levels were observed in all underweight patients and subtherapeutic levels in 12 of 13 obese patients in class II and III. A multivariate linear regression analysis revealed that body weight, cancer, and the Charlson Comorbidity Index (CCI) were independent factors influencing aFXa levels.

Our study reveals a substantial portion of medical elderly inpatients on thromboprophylaxis with non-prophylactic aFXa levels, with a notable prevalence among underweight and severely obese patients. Body weight, cancer, and CCI were identified as independent factors influencing aFXa levels, advocating for tailored thromboprophylaxis strategies. Further research is warranted to validate personalized dosing approaches and to enhance clinical decision-making. Geriatr Gerontol Int 2024; 24: 587-594.