aPTT Mixing Studies
Use
Distinguish specific (ie, factor VIII) and nonspecific (lupus anticoagulant) inhibitors; determine heparin presence; detect single or multiple factor deficiencies
Special Instructions
This test should not be performed unless the aPTT is prolonged to 5 seconds or more above the upper end of the reference interval as accurate interpretation is compromised when the aPTT is only slightly prolonged. Patient preparation should involve avoiding anticoagulant therapy; specifically, warfarin for two weeks and heparin or direct Xa and thrombin inhibitors for three days prior to testing.
Limitations
Lupus anticoagulant sensitive reagents are used in this panel and are more responsive to the presence of lupus anticoagulants. The test will not detect individual factor deficiencies unless factor levels are critically low (25% to 45%); mild deficiencies might not be detected unless multiple factors are affected. Factor VIII elevations due to acute phase reactions can normalize a mildly extended aPTT. The aPTT is more sensitive to intrinsic pathway factor deficiencies than common pathway ones. Specific limitations apply regarding detection of certain inhibitors and deficiencies based on the patient's medication regimen and coagulation status.
Methodology
Other
Biomarkers
LOINC Codes
- 14979-9
- 5946-9
- 43734-3
- 30323-0
- 44950-4
Result Turnaround Time
2-3 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
2 mL
Minimum Volume
Not provided
Container
Blue-top (sodium citrate) tube
Collection Instructions
Collect citrated plasma samples by double centrifugation into a blue-top tube with 3.2% sodium citrate. Ensure tubes are filled to mark, invert gently six times for thorough mixing, and use a discard tube when using winged blood collection device. Separate plasma by centrifugation and transfer using a plastic pipette to a Labcorp Transpak. Freeze immediately and maintain frozen until tested.
Patient Preparation
Avoid anticoagulant therapies; specifically, avoid warfarin for two weeks and heparin or direct Xa and thrombin inhibitors for about three days prior to testing. Do not draw from an arm with a heparin lock/catheter.
Storage Instructions
Freeze.
Causes for Rejection
Severe hemolysis, improper labeling, clotted specimens, specimens diluted with IV fluids, samples thawed in transit, improper sample type, sample out of stability