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Heparin Level (Low Molecular Weight Heparin)

Item Value
Approval req'd? Approval required if results needed on evenings or weekends. If medically necessary, contact Hematology at x3-1747
Available Stat? No
Test code HEP
Test group Heparin
Performed by Parnassus Hematology
In House Availability Test run Monday-Friday
Method Chromogenic Synthetic Substrate
Collection Instructions Time to steady state: 3 doses in adults and 1 dose for pediatric patients.

Collect 4 hours after 4th dose (adults) and 4 hours after 1st dose (pediatrics)

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 (x3-1747) 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UCSF Rejection Criteria Samples collected in outdated blue top vacutainer.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 (4 hours post dose):

Enoxaparin:
Q12 dosing 0.5-1.0 U/mL
Qday dosing 1.0-2.0 U/mL
Prophylactic dosing 0.2-0.4 U/mL


Dalteparin:
Q12 dosing 0.6 U/mL
Qday dosing 1.05 U/mL


Tinzaparin:
Qday dosing 0.85 U/mL


These are general guidelines only. Detailed recommendations for heparin therapy and monitoring are available through the UCSF Comprehensive Hemostasis and Antithrombotic Service (CHAS), which can be contacted at pager 443-4023.
Critical value
Low Mol. Weight heparin >2.0 U/mL
Synonyms Monitoring Anticoagulation; Low Molecular Weight Heparin; LMW Heparin; LMWH; Enoxaparin; Tinzaparin; Dalteparin; Danaporoid; Anti Factor 10a; Anti factor Xa; Factor 10a; Lovenox
Turn around times 1-3 days
Additional information The utility of measuring LMW heparin levels is limited to a few clinical settings. Common indications for monitoring patients receiving LMW heparin include renal insufficiency, clinical obesity, weight < 50 kg or pregnancy.

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 specific medication, the disease, and the treatment intensity desired. Recommendations for heparin therapy and monitoring are available through the UCSF Hematology Consultation service, which can be contacted at pager 443-4276.

Click here for A guide on Drug Level Monitoring
LOINC code 3271-4
Last Updated 5/1/2014 3:21:57 PM
Entry Number 471
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