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If you have additional questions regarding this test, please call: 415-353-1667
|Approval req'd?||No, except for testing outside of stated test availability, contact Hematology at x31747|
|Performed by||Parnassus Hematology|
|In House Availability||Monday - Friday 0800-1600. Approval required for testing outside of these hours.|
|Method||Mechanical clot detection asay|
|Collection Instructions||1. Peripheral stick required as heparin will interfere with the test.
2. Collect 1 blue top filled to full extent of vacuum (2.7 mL blood). Check the expiration date on the label of the blue top vacutainer before drawing the patient.
3. 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.
4. 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.
5. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.
6. 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||1.0 mL plasma|
|Min. Volume||0.5 mL plasma|
|UCSF Rejection Criteria||QNS, hemolyzed or clotted sample.|
|Processing notes||Deliver sample immediately to Hematology for processing|
|Normal range||Therapeutic anticoagulation: 0.5-2.0 µg/mL (mcg/mL)
Note: these values may not be applicable to intra-operative anticoagulation. See 'Additional information'
|Critical value||> 2.0 µg/mL|
|Synonyms||Direct thrombin inhibitor|
|Turn around times||1-3 days|
|Additional information||The information contained herein is applicable to patients receiving argatroban in the setting of heparin induced thrombocytopenia. If argatroban is being utilized in other settings, including percutaneous coronary interventions, it is suggested that the Hematology Consultation service (pager: 443-4276) and a physician in the coagulation laboratory (353-1747) be contacted.
Argatroban is usually monitored by the activated PTT. Rarely, however, plasma argatroban levels should be measured to give a more accurate estimate of clinical anticoagulation.
Lupus anticoagulants can prolong the PTT at baseline, or impact the PTT after a patient has begun heparin therapy. If a patient being treated with argatroban is known or suspected to have a lupus anticoagulant, an argatroban level and an aPTT should be sent simultaneously. If review of results of simultaneous argatroban and PTT measurements indicates that the patient's lupus anticoagulant is causing an artifactual PTT prolongation, subsequent monitoring with argatroban levels is indicated.
The manufacturer of argatroban, GlaxoSmithKline, provides complete prescribing information on its website: http://www.argatroban.com/argatroban_indications.htm, including information on the association of plasma argatroban levels and the activated PTT. A portion of the relevant information from this March 2009 document is summarized in the following information and in the graph shown in the Image portion of this web-page:
"Laboratory Tests: Anticoagulation effects associated with Argatroban infusion at doses up to 40 mcg/kg/min correlate with increases of the activated partial thromboplastin time (aPTT)."
"Dosage Adjustment: After the initial dose of Argatroban, the dose can be adjusted as clinically indicated (not to exceed 10 mcg/kg/min), until the steady-state aPTT is 1.5 to 3 times the initial baseline value (not to exceed 100 seconds)"
Patients for whom a lupus anticoagulant influences the PTT must be monitored with argatroban levels. Therapeutic levels are not recommended by the manufacturer, but the manufacturer does provide this graph that shows a relationship among representative PTT levels, ACT levels, infusion rates, and plasma Argatroban levels:
In the graph, a 0.4 microgram/mL argatroban level corresponded to approximately 1.6x the baseline PTT whereas a 2.0 microgram/mL argatroban level corresponded to approximately 2.6x the baseline PTT.
At UCSF we have assessed the sensitivity of our current PTT reagent to argatroban in June 2009. In a plasma sample spiked ex vivo with argatroban, we observed that 0.5 microgram/mL argatroban resulted in a PTT 1.7x baseline, 2.0 microgram/mL resulted in a PTT 2.5x baseline, 2.5 microgram/mL resulted in a PTT 2.7x baseline, and 3.0 microgram/mL resulted in a PTT 2.9x baseline. These results are generally similar to the information provided by the manufacturer and to the results of two prior UCSF ex vivo spiking studies (performed in January and in March 2006).
On the basis of the information available, argatroban levels of 0.5-2.0 micrograms/mL can be considered therapeutic. These levels correspond to 1.7x-2.5x baseline PTT in a patient without a lupus anticoagulant, which is within the manufacturer's recommended therapeutic PTT of 1.5x-3.0x patient baseline.
For adult patients without lupus anticoagulants an argatroban order form is available and should be utilized. The therapeutic PTT as of November 2009 was 50-69.9 seconds. For patients in whom the PTT cannot be used for monitoring, a derivative algorithm, based on a therapeutic target of 0.5-2.0 micrograms/mL, should be used for monitoring and dose adjustment, as clinically indicated. It is suggested that the Hematology Consultation service (415-443-4276) be contacted for recommendations regarding an appropriate algorithm for monitoring and dose adjustment in these patients.
The presence of heparin will interfere with the argatroban assay and can produce an erroneously elevated argatroban test result.
GlaxoSmithKline, provides in complete prescribing information on its website accessed November 2010:Click here for Link
|LDT or Mod FDA?||Yes|
|Last Updated||10/4/2013 9:59:50 PM|
|Image caption||Relationship at Steady State Between Argatroban Dose, Plasma Argatroban Concentration and Anticoagulant Effect.
Suggested therapeutic level of 0.5-2.0 micrograms/mL is compatible with data shown in this graph as well as with UCSF analysis described in Additional Information