Anti-Xa Assay Correlation to the Efficacy and Safety of Enoxaparin in the Treatment of Pulmonary Embolism

Background: Enoxaparin is one of the LMWH that has been used for long time in the treatment of acute pulmonary embolism. In this study, we will monitor anticoagulant therapy by anti-Xa assay and correlate its level to the efficacy and safety of enoxaparin in the treatment of pulmonary embolism. Methods: The study was conducted on 42 patients in ICU diagnosed to have pulmonary embolism by CT pulmonary angiography and treated by subcutaneous enoxaparin 1 mg/kg every 12 hours. Anticoagulant therapy was followed by anti-Xa assay done 4 hours after the third dose of subcutaneous enoxaparin and the results were correlated to the clinical outcome of the patients as regards complications (recurrent pulmonary embolism, bleeding, low platelet count and death). Results: According to anti-Xa assay, we divided the patients into three groups. Group I with anti-Xa level < 0.5 IU/mL, group II with anti-Xa level ≥ 0.5 and < 1.2 IU/mL and group III with anti-Xa level ≥ 1.2 IU/mL. 9 patients were in group I, 22 patients were in group II and 11 patients were in group III. There was no significant difference between the three groups as regards age, sex, BMI and underlying risk factors for pulmonary embolism. Serum creatinine level and pulmonary artery pressure were significantly higher in group I than in group II and III. The incidence of recurrent pulmonary embolism was significantly higher in group I than in group II and III with 7 out of 9 patients in group I had recurrent pulmonary embolism compared with only 4 out of 22 and 1 out of 9 in group II and III respectively. The mortality rate was significantly higher in group I than in group II and III with 3 recorded death cases in group I compared with zero recorded cases in group II and III. There was no significant difference between the three groups as regards thrombocytopenia and major bleeding complications. Conclusion: Anti-Xa assay is a good and reliable test for monitoring the efficacy of LMWH therapy using enoxaparin for patients with pulmonary embolism as regards recurrence and mortality rates of pulmonary embolism but it will not monitor safety of enoxaparin therapy as regards incidence of thrombocytopenia and bleeding complications. The study was registered on www.clinicaltrials.gov, Registration ID: NCT02977013. Registered November 27, 2016.