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Lab Manual for Moffitt-Long and Mount Zion

Lab Manual for SFGH

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Heparin Level (Unfractionated heparin)

Item Value
Approval req'd? Approval required if results needed on evenings or weekends. If medically necessary, contact Hematology at 415-353-1747
Available Stat? No
Test code UFHEP
Test group Heparin
Performed by Parnassus Hematology
In House Availability Monday - Friday
Method Chromogenic Synthetic Substrate
Collection Instructions 1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

Indicate exact brand and type of heparin or heparinoid being used on requisition.

For patients with Hct's ≥ 55% please contact Hematology (415-353-1747) to obtain blue top tubes with adjusted citrate volumes in order to maintain the proper citrate to plasma ratio for coagulation studies.
Container type Blue top filled to full extent of vacuum
Amount to Collect 2.7 mL blood
Sample type Citrated plasma
Preferred volume 1 mL plasma
Min. Volume 0.5 mL plasma
UCSF Rejection Criteria Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected
Processing notes Deliver specimen to Hematology lab ASAP for processing.

Separate plasma at 5000 rpm for 8 min. Make two separate 1 mL aliquots in plastic tubes and freeze at -20C
Units anti-Xa U/mL
Normal range Therapeutic:

UFH by infusion 0.3-0.7 anti-Xa U/mL
Critical value > 0.70 anti-Xa U/mL
Synonyms Monitoring Anticoagulation; UFH; Unfractionated heparin; Anti Factor 10a; Anti factor Xa
Turn around times 1-3 days
Additional information The utility of measuring heparin levels is limited to 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 Stachrom Heparin assay uses exogenous activated factor Xa and exogenous antithrombin. This combination can overestimate the in vivo therapeutic effect of heparin and low-molecular weight heparin in the setting of severe antithrombin deficiency.
In addition to congenital antithrombin deficiency, the possibility of antithrombin deficiency should be considered in the setting of prematurity, nephrotic syndrome, cirrhosis, L-asparaginase therapy, disseminated intravascular coagulation, microangiopathic hemolytic anemia, venoocclusive disease, or other severe debilitating illness. In these clinical settings, consideration could be made for ordering an antithrombin level to confirm accurate monitoring of anticoagulant effect by the anti-Xa assay.

The appropriate therapeutic range will vary with the disease and the treatment intensity desired. An overview of recommendations is available in the laboratory manual for reference purposes only in the entry: Heparin Laboratory/Dosing Algorithm. Recommendations for therapy and monitoring are also available through the Hematology consultation service, pager 443-4276.

Click here for A guide on Drug Level Monitoring
Last Updated 12/16/2013 10:31:44 AM
Entry Number 1183
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