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Clinical Significance
Clinical Significance
Partial Thromboplastin Time, Activated - The aPTT is a screening test that will detect deficiencies or inhibitors to the intrinsic (Factors VIII, IX, XI and XII) and common (Factors II, V, X and fibrinogen) pathway coagulation factors.
Test Details
Test Details
Methodology
Methodology
Photo-Optical Clot Detection
Reference Range(s)
Reference Range(s)
≤6 months
Not established
>6 months
23-32 sec
Flagging not provided. Pediatric reference intervals have not been established. Based on published literature, the adult reference interval (23-32 seconds) is generally applicable down to approximately 6 months of age with younger patients having a slightly higher upper limit by several seconds.
Alternative Name(s)
Alternative Name(s)
APTT, PTT
Preferred Specimen(s)
Preferred Specimen(s)
One full unopened 3.2% sodium citrate (light blue-top) tube
Alternative Specimen(s)
Alternative Specimen(s)
1 mL frozen plasma
Minimum Volume
Minimum Volume
0.3 mL
Collection Instructions
Collection Instructions
Unopened light blue-top tube: Correct ratio of blood to citrate is critical. Do not overfill or underfill collection tube. Mix by inversion 4 times. For non-heparinized patients, maintain specimen at room temperature. Do not uncap. Stable 24 hours at room temperature.
Platelet-poor plasma: Centrifuge light blue-top tube 15 minutes at approximately 1500 g within 60 minutes of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial. Plasma must be free of platelets (<10,000/mcl). Freeze immediately and ship on dry ice.
Whole blood: The tubes should be at 100% +/- 10% fill volume in order to obtain the correct ratio.
Transport Container
Transport Container
3.2% sodium citrate (light blue-top) tube
Transport Temperature
Transport Temperature
Room temperature
Specimen Stability
Specimen Stability
Unopened light blue-top tube
Room temperature: 24 hours
Refrigerated: Unacceptable
Frozen: Unacceptable
Separated platelet-poor plasma
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 14 days
Reject Criteria
Reject Criteria
Gross hemolysis • Grossly lipemic • Improper blood to citrate ratio • Clotted • High hematocrits • Thawed plasma received room temperature or refrigerated
Setup Schedule
Setup Schedule
Set up: Mon-Sat (All shifts); Sun (STAT only); Report available: 1 day
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