2 hours
Test Updated:
Heparin, Unfractionated
Heparin, Standard
Unfractionated Heparin
Standard Heparin
UFH Anti-Xa
Anti-Xa, UFH
Heparin (UFH) Anti-Xa Assay
Anti-Xa Unfractionated Heparin
Factor Xa Inhibition
Coagulation Factor Xa Inhibition
HEPARIN
Chromogenic Xa
Xa Chromogenic
UNFH
Factor 10a Inhibition
Anti-10a UFH
Looking to order a test?
We’ve provided helpful links to make ordering easy.
Find a RequisitionAll specimens should be accompanied by a requisition.
Submitting SpecimensLearn about how to properly label and where to ship specimens.
Order Kits and SuppliesMLabs provides all the supplies necessary for the collection of specimens.
Test FAQVisit our provider FAQ and learn about common questions to ordering tests.
Test Overview
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.
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
Specimen Requirements
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.
