This test is intended only for patients receiving unfractionated heparin by infusion. Other anti-Xa medications, such as low molecular weight heparins (e.g., enoxaparin, dalteparin, tinzaparin) and direct anti-Xa inhibitors (e.g., apixaban, rivaroxaban, edoxaban) may interfere with this test. Please check lab manual for appropriate tests specific to the anticoagulant the patient is receiving.
Available Stat
Yes
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Performed
24 hours per day, 7 days per week
Methodology
Chromogenic
Reported
1 hour from receipt in Hematology
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
Synonyms
Anti-Xa Level
Sample Type
Blood
Collect
Blue top filled to full extent of vacuum (3.2% sodium citrate)
Amount to Collect
2 mL blood
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Remarks
Deliver specimen to lab immediately for processing
Stability (from collection to initiation)
2 hours
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Test Code
UNHEP
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Specimen Preparation
Deliver sample immediately to Hematology Lab
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Stability (from collection to initiation)
2 hours
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Units
U/mL
Reference Interval
Therapeutic:
UFH by infusion: 0.3 - 0.7 anti-Xa U/mL
Critical Values
> 0.70 anti-Xa U/mL
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
CPT Codes
85520
LOINC Codes
3274-8
Available Stat
Yes
Ordering Recommendations
This test is intended only for patients receiving unfractionated heparin by infusion. Other anti-Xa medications, such as low molecular weight heparins (e.g., enoxaparin, dalteparin, tinzaparin) and direct anti-Xa inhibitors (e.g., apixaban, rivaroxaban, edoxaban) may interfere with this test. Please check lab manual for appropriate tests specific to the anticoagulant the patient is receiving.
Test Code
UNHEP
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Performed
24 hours per day, 7 days per week
Methodology
Chromogenic
Remarks
Deliver specimen to lab immediately for processing
Collect
Blue top filled to full extent of vacuum (3.2% sodium citrate)
Amount to Collect
2 mL blood
Sample Type
Blood
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Specimen Preparation
Deliver sample immediately to Hematology Lab
Units
U/mL
Reference Interval
Therapeutic:
UFH by infusion: 0.3 - 0.7 anti-Xa U/mL
Critical Values
> 0.70 anti-Xa U/mL
Synonyms
Anti-Xa Level
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Stability (from collection to initiation)
2 hours
Reported
1 hour from receipt in Hematology
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
CPT Codes
85520
LOINC Codes
3274-8
Ordering
Ordering Recommendations
This test is intended only for patients receiving unfractionated heparin by infusion. Other anti-Xa medications, such as low molecular weight heparins (e.g., enoxaparin, dalteparin, tinzaparin) and direct anti-Xa inhibitors (e.g., apixaban, rivaroxaban, edoxaban) may interfere with this test. Please check lab manual for appropriate tests specific to the anticoagulant the patient is receiving.
Available Stat
Yes
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Performed
24 hours per day, 7 days per week
Methodology
Chromogenic
Reported
1 hour from receipt in Hematology
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
Synonyms
Anti-Xa Level
Collection
Sample Type
Blood
Collect
Blue top filled to full extent of vacuum (3.2% sodium citrate)
Amount to Collect
2 mL blood
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Remarks
Deliver specimen to lab immediately for processing
Stability (from collection to initiation)
2 hours
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Processing
Test Code
UNHEP
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Specimen Preparation
Deliver sample immediately to Hematology Lab
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Stability (from collection to initiation)
2 hours
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Result Interpretation
Units
U/mL
Reference Interval
Therapeutic:
UFH by infusion: 0.3 - 0.7 anti-Xa U/mL
Critical Values
> 0.70 anti-Xa U/mL
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
Administrative
CPT Codes
85520
LOINC Codes
3274-8
Complete View
Available Stat
Yes
Ordering Recommendations
This test is intended only for patients receiving unfractionated heparin by infusion. Other anti-Xa medications, such as low molecular weight heparins (e.g., enoxaparin, dalteparin, tinzaparin) and direct anti-Xa inhibitors (e.g., apixaban, rivaroxaban, edoxaban) may interfere with this test. Please check lab manual for appropriate tests specific to the anticoagulant the patient is receiving.
Test Code
UNHEP
Performing Lab
Parnassus Hematology, Mission Bay Hematology
Performed
24 hours per day, 7 days per week
Methodology
Chromogenic
Remarks
Deliver specimen to lab immediately for processing
Collect
Blue top filled to full extent of vacuum (3.2% sodium citrate)
Amount to Collect
2 mL blood
Sample Type
Blood
Preferred Volume
1 mL plasma
Minimum Volume
0.5 mL plasma
Unacceptable Conditions
Hemolysis, Icterus, Lipemia
Under-filled or Over-filled tubes
Clotted
Specimen Preparation
Deliver sample immediately to Hematology Lab
Units
U/mL
Reference Interval
Therapeutic:
UFH by infusion: 0.3 - 0.7 anti-Xa U/mL
Critical Values
> 0.70 anti-Xa U/mL
Synonyms
Anti-Xa Level
Storage/Transport Temperature
Deliver whole blood at room temperature
Plasma acceptable on dry ice and stored -20 to -80C
Stability (from collection to initiation)
2 hours
Reported
1 hour from receipt in Hematology
Additional Information
The utility of measuring heparin levels has been demonstrated in a few clinical settings. Patients receiving unfractionated heparin require heparin levels if there is heparin resistance (adults requiring more than 35,000 units/day) or if a lupus anticoagulant is present; in such conditions the PTT may not be an accurate indicator of anticoagulation.
The STA- Liquid anti-Xa method is a one-step reaction where factor Xa is added to the plasma-substrate mixture. Two reactions take place simultaneously,
-Hydrolysis of the substrate by factor Xa
-Inhibition of factor Xa by the heparin-antithrombin complex*.
After the necessary period of time for the competitive reaction to reach equilibrium, the quantity of pNA that is released is inversely proportional to the concentration of heparin present in the test medium.
*The heparin-antithrombin complex is made up from the heparin medication and the patient’s endogenous antithrombin.
Note that a similar methodology used for detecting other anti-Xa medications; however, the calibration curve is distinct for each drug. Therefore, while a positive result from this test (anti-Xa Heparin level) indicates the presence of anti-Xa activity, the exact level of any drug other than unfractionated heparin cannot be assessed.
The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available on the UCSF Carelinks webpage for reference purposes only. Recommendations for therapy and monitoring are also available through the Hematology consultation services: for adults, pager 443-4276, for pediatrics pager 443-6966.
