Anti Xa for Heparin Infusion

Regular Intensity Heparin Therapy: 0.3-0.7 IU/mL

Low Intensity Heparin Therapy: 0.3-0.5 IU/mL

For more information, visit UW Medicine Anticoagulation Services

HIXA results will be falsely elevated in the presence of direct factor Xa inhibitors (such as apixaban, rivaroxaban, edoxaban) or low molecular weight heparin.

Low antithrombin level (<70%) may cause an underestimation of the heparin level.

This assay is insensitive to hemoglobin (up to 0.15 g/dL), conjugated bilirubin (up to 28.8 mg/dL), unconjugated bilirubin (up to 13.8 mg/dL), and triglycerides (up to 690 mg/dL).

Specimen must be processed/centrifuged within one hour of collection. After initial centrifugation the test is viable on samples up to 4 hours old. If testing cannot be done within 4 hours, remove and re-spin plasma, decant upper layer of plasma and freeze until testing can be performed.

Sodium citrate samples at UW-NW must be centrifuged within one hour and are stable at room temperature up to 2 hours. If there is a delay greater than 1 hour, re-spin plasma, remove upper layer of plasma and freeze until testing can be performed.

Outside Laboratories: Within one hour of collection, centrifuge sample for 10 minutes, remove plasma & re-spin for another 10 minutes. Remove upper layer of plasma and freeze (1 mL) @ -20 ˚C to - 80 ˚C. Transport frozen on dry ice.

Note: Samples that are drawn through a heparinized line may be contaminated by the heparin in the line. HIXA results on this sample would reflect the anti-Xa activity of the heparin in the patient as well as the heparin from the line and may be erroneously increased.

Samples containing platelet clumps or hemolysis due to difficult blood draws may show decreased heparin activity due to in vitro platelet activation. If results are unexpectedly low, redraw the sample and repeat the test.

Take whole blood specimen to COAG Lab

For HIXA as add-on test to previous sample, check with coag testing bench personnel to determine if testing can be performed due to specimen stability or volume issues