What is anti factor Xa activity?
What is anti factor Xa activity?
The plasma anti-Xa assay is a laboratory test that indirectly measures the activity of heparins. It is predominantly used for monitoring patients treated with low molecular weight heparins, particularly when dosing at the extremes of weight and in patients who are pregnant, critically ill or have renal impairment.
What does high anti factor Xa mean?
If the heparin anti-Xa result is high, then the person may be getting an excessive dose and/or not be clearing the drug at an expected rate and may be at an increased risk for excessive bleeding.
When should anti-Xa be drawn?
Heparin anti-Xa levels should be drawn six hours after initiation of unfractionated heparin therapy or change in dose, whereas, with low molecular weight heparin, levels should be drawn six hours after administration when given once daily and three to four hours when administered twice daily.
What is an anti-Xa test?
The test is used to monitor heparin therapy to ensure that a person is receiving sufficient heparin for anticoagulation without causing excess bleeding. Since the test involves a chemical reaction color change (colorimetric), it is also known as chromogenic anti-Xa assay or anti-Xa assay, chromogenic.
What is a normal anti-Xa level?
Anti-Xa levels should be checked at their peak at 4 hours after dosing (both q12 and q24 variations). Reference ranges are not clinically validated and can vary by facility and indication for use. Suggested “therapeutic range” is usually 0.6-1.0 units/mL.
What does it mean if anti-Xa is low?
A low level of anti-Xa may be seen if the specimen is not collected at the right time or if there was a delay in separation of the plasma from the cellular component of the blood.
What is normal anti-Xa level?
What can affect anti-Xa levels?
Anti-Factor Xa for Monitoring of Unfractionated Heparin Therapy
| Influencing factor | Antifactor Xa | |
|---|---|---|
| Biologic | Antithrombin deficiency | ↓ |
| Increased levels of acute phase reactants (factor VIII or fibrinogen) | ? | |
| Increased heparin-binding proteins (inflammation, infection, malignancy) | ↓ | |
| Obesity (i.e. increased volume of distribution) | ↓ |
What is the goal anti-Xa level?
The peak anti-factor Xa (anti-Xa) level is the recommended test for monitoring enoxaparin efficacy. Blood samples should be withdrawn about 3–5 hours after dose administration. The target peak anti-Xa level for prophylactic doses of enoxaparin is 0.2–0.5 IU/mL.
What causes low anti-Xa level?
Icteric, lipemic, and/or hemolyzed samples can interfere with chromogenic methods, resulting in decreased reported anti-Xa levels.
