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aPTT Mixing Study

Justification

Mixing studies are performed to determine whether prolongations in coagulation screening tests are due to coagulation factor deficiencies or the presence of an inhibitor. This can help direct further follow-up testing.

STAT: < 24 hours (7 days a week)

Clot-based

Draw Tube: Blue Top

Sample Type: Citrated Plasma

Specimen Requirements

Sample Type Volume Required Minimum Volume Stability
PREFERRED Citrated Plasma 1mL 0.5mL Frozen (-20C): 2 weeks
Frozen (-80C): 6 months
ALTERNATIVE - - - -
REJECTION CRITERIA Thawed in transit, refrozen or clotted sample
SPECIAL INSTRUCTIONS -

General Information

METHODOLOGY Clot-based
STAT TAT < 24 hours (7 days a week)
STAT TAT Performance > 90% of results released in 24 hours 7 days a week
ROUTINE TAT < 24 hours (M-F)
ALTERNATIVE NAMES PTT Mixing Study
DESCRIPTION aPTT is performed on immediate and incubated mixtures of patient and normal pooled plasmas. If the prolonged aPTT corrects upon immediate and incubated mixture with normal pooled plasma, follow up with specific factor activity assays. If the prolonged aPTT corrects upon immediate mixture with normal pooled plasma, but fails to correct after incubation, a temperature-dependent specific factor inhibitor may be present and a follow up Factor VIII (8) Activity level and Factor VIII (8) Inhibitor Titer may be indicated. If the prolonged aPTT fails to correct upon immediate mixture with normal pooled plasma, assess for the presence of an anticoagulant such as heparin or a lupus anticoagulant.
LIMITATIONS -
NORMAL RANGE Interpretation
ASSOCIATED TESTING -
REFERENCES -
SAMPLE REPORT Upon request
NEW YORK STATE APPROVED -

Test Codes

ORDER CODE P3077
CPT CODE 85730, 85732
LOINC CODE 14979-9, 5946-9, 44950-4