In this way, the chromogenic
anti-Xa assay is a versatile anticoagulation monitoring and measurement assay with automation capability and ease of use to support widespread routine use.
With better outcomes from the anti-Xa assay (Paluri et al., 2014), its use may become more common.
Therapeutic Ranges for aPTT and Anti-Xa Assay at UPMC Heparin Order Set Anti-Xa Therapeutic Ranges aPTT (seconds) (units/ML) DVT/PE 0.3-0.7 68-106 UA/NSTEMI 0.3-0.6 68-96 Afib/post-op 0.3-0.45 68-82 Stroke, EP, VAD, 0.25-0.35 59-72 High risk for bleeding Anti Xa Supratherapeutic aPTT (seconds) Range (units/ML) Stroke, EP, VAD, 0.25-0.35 59-72 High risk for bleeding Notify MD if [greater than or equal to] 0.7 > 106 (stroke, EP, VAD, high risk bleed) > 1 > 125 (all others) Notes: A-fib = atrial fibrillation postoperatively, DVT = deep vein thrombosis, EP = electrophysiology, NSTEMI = non-ST elevation myocardial infraction, PE = pulmonary embolus, UA = unstable angina, VAD = ventricular assist device Reprinted with permission from Donahue et al., 2016.
Generally,
anti-Xa assays are readily available and widely used and can be relatively easily calibrated to accurately measure factor Xa inhibitor concentrations.
Comparison of calibrated chromogenic
anti-Xa assay and PT tests with LC-MS/MS for the therapeutic monitoring of patients treated with rivaroxaban.
Bilirubin and free Hb also affected the
anti-Xa assay: anti-Xa activity decreased by 0.03 to 0.05 IU/mL with each increment of free Hb concentration by 100 mg/dL (Figure 2, A) or with bilirubin increment of 6 mg/dL (Figure 2, B).
To confirm the heparin concentration, heparin was also measured with an
anti-Xa assay on the MDA (BioMerieux).
The correlations between clotting time values and actual heparin concentrations as determined by the
anti-Xa assay were poor for each of the tests evaluated.
As shown in Table 1, the Hepcon and potentiometric sensor-based methods show good correlation between each other, and reasonable correlation with heparin measurements with the chromogenic
anti-Xa assay. Minimal bias was found in heparin measurements between the heparin and protamine sensors (0.17 kU/L; P = 0.001), and between the protamine sensor and the Hepcon (0.08 kU/L; P = 0.02).
