Evaluation of a novel point-of-care enoxaparin monitor with central laboratory anti-Xa levels

Background: Measurement of enoxaparin's anticoagulant activity has been limited to specialized coagulation laboratories and has been impractical for areas needing rapid results, such as during coronary angioplasty. A new point-of-care device, Rapidpoint® ENOX®, was recently developed to measure clotting times with enoxaparin use. Objectives: To correlate ENOX times with anti-Xa levels among patients receiving enoxaparin. Methods: A total of 166 patients receiving enoxaparin for the prevention of deep venous thrombosis or as treatment during acute coronary syndromes or angioplasty were prospectively studied. Citrated and non-citrated whole-blood (CWB and NCWB) samples were obtained at baseline and peak enoxaparin activity. ENOX times were measured with whole-blood, and the Stachrom® anti-Xa assay was performed on the plasma from the remainder of the samples. The Pearson correlation coefficient was used to assess the relationship between these two assays. Results: There was a strong linear correlation between the ENOX times and the anti-Xa activities for both CWB (r=0.89, p<0.001) and NCWB (r=0.82, p<0.001) when considering all 332 samples (baseline and peak). When baseline samples were excluded, the correlation remained strong for CWB ENOX times and anti-Xa levels (r=0.84, p<0.001), but was only moderate for NCWB (r=0.73, p<0.001). A CWB ENOX time of ≤160 s corresponded to anti-Xa level of ≤0.5 IU/ml in 95% (188/197) of patients. A CWB ENOX time ≥200 s corresponded to anti-Xa levels ≥0.8 IU/ml in 96% (93/96) of patients. Conclusions: Rapidpoint® ENOX® times correlate strongly to anti-Xa activities measured by the Stachrom® Heparin Assays for citrated whole-blood samples. This novel test can be used for rapid bedside measurements of enoxaparin anticoagulant activity.