Heparin (UFH) Anti-Xa Assay
Anti-Xa Unfractionated Heparin
Factor Xa Inhibition
Coagulation Factor Xa Inhibition
Factor 10a Inhibition
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Chromogenic Substrate Assay
Used to monitor treatment with unfractionated (standard) heparin.
The therapeutic range is 0.3 - 0.7 IU/mL. Critical value: > 1.0 IU/ml.
Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within one hour of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic vial, and freeze the specimen within 1 hour of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.