Comparison of Anti-Xa factor assay and ACT for monitoring the anticoagulation effects of low-molecular-weight heparins in elderly patients

Background Since the routine method of anti-Xa factor assay cannot be used as a bedside test, this study was designed to investigate the correlation between activated clotting time (ACT) detected by a Sonoclot Analyzer and the anti-Xa factor assay. Methods A total of 84 patients older than 60 years with acute medical diseases admitted in Beijing Tongren Hospital from July to December, 2010 who were given enoxaparin or nadroparin subcutaneously for at least 5 days were enrolled and, divided into two groups. The ACS group (n=52) was dosing generally 1 mg/kg twice a day, but with a half dose in the condition of serum creatine above 177 μmmol/l. The remainder as the VTE high risk group (n=32) received 40 mg once daily. Another 44 healthy subjects as the control group received no anticoagulants. Blood samples were collected at the second and the fifth days after LMWH administration for detecting ACT and plasma anti-Xa factor activity (AFXa). ACT was detected immediately, while AFXa were detected by Factor Xa ELISA kit within 3 months. Data was analysed by different diseases, kinds of LMWH, gender, ages and different renal functions. Results (1) The AFXa and ACT values were significantly higher in the group that received LMWHs (0.806±0.050 IU/ml, 285±125 s) than in the control group (0.617±0.042 IU/ml) and the ACT reference range (119–195 s) (p