Assay

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ASSAY. A chemical examination of metals, by which the quantity of valuable or precious metal contained in any mineral or metallic mixture is ascertained. 2. By the acts of Congress of March 3, 1823, 3 Story's L. U. S. 1924; of June 25, 1834, 4 Shars. cont. Story's L. U. S. 2373; and of June 28, 1834, Id. 2377, it is made the duty of the secretary of the treasury to cause assays to be made at the mint of the United States, of certain coins made current by the said acts, and to make report of the result thereof to congress.

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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).