Prothrombin Time (PT) Mixing Study
Also known as: PT Mixing Study
Use
Distinguish between circulating inhibitor and coagulation factor deficiency when PT is prolonged
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. Ideally, the patient should not be on anticoagulant therapy; avoid warfarin for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Limitations
Tests could give false results in cases of severe hemolysis, improper labeling, clotted specimens, or specimens diluted with IV fluids. Samples thawed in transit, improper sample types, or samples that are out of stability may also lead to rejection. Additionally, the presence of weak inhibitors that normal plasma can overcome could lead to a temporary correction, which may obscure the true cause of the test prolongation.
Methodology
Automated Analyzer
Biomarkers
LOINC Codes
- 33356-7
- 5902-2
- 5959-2
- 5902-2
- 5959-2
- 33356-7
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
2 mL
Minimum Volume
1 mL
Container
Blue-top (sodium citrate) tube
Collection Instructions
Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio. The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood.
Patient Preparation
Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability