Background:
The activated partial thromboplastin time (aPTT) is commonly used to monitor the anticoagulant effects of unfractionated heparin (UFH). Heparin-responsiveness of aPTT reagents may change from lot to lot and among different reagents used on different instrument platforms.
UC Irvine’s Laboratory will be switching to a new lot of aPTT reagent on Wednesday, June 17, 2020. This new lot of reagent shows a different responsiveness to unfractionated heparin compared to the current lot. Changes to the heparin therapeutic range are shown in the table below:
Unfractionated Heparin (UFH) Goal |
Therapeutic Range |
anti-Xa UFH Target |
aPTT Target
(CURRENT LOT) |
aPTT Target
(NEW LOT) |
ACS/DVT/PE and
most indications |
0.3 - 0.7 units/ml |
65-110 seconds |
70-115 seconds |
Stroke (recent ischemic stroke or
hemorrhagic stroke in the last 2 weeks) |
0.2 - 0.37 units/ml |
55-70 seconds |
55-75 seconds |
Please also refer to the Heparin per Pharmacy Protocol via the Hospital SharePoint for additional information.
As a reminder, anti-Xa activity assay (lab test code UHEP) is an acceptable alternative method to monitor unfractionated heparin therapy.
Effective date: June 17, 2020
Specimen requirement and testing information:
Specimen: Collect 2.7 mL blood in a light blue-top (3.2% sodium citrate) plastic tube
Test code: PTT
Minimum stability (collection to initiation of testing):
Ambient: 4 hours
Refrigerated: Unacceptable
Frozen: 2 weeks
Turnaround time (TAT):
STAT: 60 minutes
Routine: 2-4 hours
Test set up frequency: Daily
Specimen required: 1.0 mL citrated plasma
Minimum volume: 0.5 mL citrated plasma
Rejection criteria: Specimens that exceed stated stability, unlabeled/mislabeled/mismatched specimens, specimens submitted in leaking containers, clotted, hemolyzed or under-filled tubes, specimens submitted in glass tubes
A summary of all tests offered by our laboratory services can be found here: http://www.pathology.uci.edu/services/index.asp
Sincerely,
Jennifer S. Woo, MD
Director
Hematology/Coagulation
Parmis Khatibi, PharmD, CACP, CTTS, APh
Anticoagulation Pharmacist Specialist
Edwin S. Monuki, MD, PhD
Chair
Department of Pathology & Laboratory Medicine |