Utility of Anti-Xa Levels in Lung Transplant Recipients on Apixaban

IntroductionThe utility of routine monitoring of apixaban anti-Xa levels in lung transplant recipients remains uncertain due to insufficient data. This population presents unique characteristics including altered renal function and medication interactions that may affect serum apixaban concentrations. Project Aims: This study evaluated the correlation between apixaban anti-Xa levels and specific covariates in lung transplant recipients to identify influential variables.DesignData from adult inpatient lung transplant recipients who had received apixaban between August 8, 2021, and December 12, 2023, at a single transplant center was analyzed. Multiple linear regression analysis was conducted, adjusting for gender, age, serum creatinine, weight, azole antifungal use, package insert deviation, dose, and level timing. Safety was assessed based on thrombotic events and major bleeding incidents during hospital admission.ResultsSeventy-eight unique apixaban anti-Xa levels were analyzed. Higher age, serum creatinine, and apixaban dose, as well as closer level timing to administration and female gender correlated with elevated anti-Xa levels. Thrombotic events occurred in 27% of cases, with one major bleeding incident.ConclusionApixaban anti-Xa levels correlated with age, serum creatinine, dose, and timing of administration in lung transplant patients. This questions the utility and necessity of obtaining apixaban anti-Xa levels despite the unique patient cohort. Larger trials are needed to assess the absolute correlation of anti-Xa levels with bleeding and thromboembolic outcomes in this population.