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Activated Partial Thromboplastin Time
MessagePerformed in the Coagulation Department
Test Code
APTT
Alias/See Also
PTT
Preferred Specimen
3.2% sodium citrate - blue top tube
Other Acceptable Specimens
None
Instructions
The light blue capped tubes, containing 3.2% buffered sodium citrate, used for coagulation testing must be allowed to fill completely (after filling a small air space will normally be present). We cannot accept a short filled tube. For patients having a hematocrit greater than 55%, contact the hospital coagulation department to obtain a special collection tube.
Transport Temperature
Ambient
Specimen Stability
Unopened Collection Tube - Vacuum in-tact tube ≤ 4 hours
Opened Collection Tube - Vacuum broken ≤ 4 hours
Frozen - Separate plasma with 4 hours - 2 weeks at -20°C
Plasma should only be thawed once
Test within 2 hours of thawing
Opened Collection Tube - Vacuum broken ≤ 4 hours
Frozen - Separate plasma with 4 hours - 2 weeks at -20°C
Plasma should only be thawed once
Test within 2 hours of thawing
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
- Clotted
- Serum received instead of Sodium Citrate plasma
- Specimen past stability
- Frozen plasma received thawed
- Underfilled or Overfilled, blood/anticoagulant ratio must be 9/1; specimens must be between 90% -110% full
- Collected in a 3.8% Sodium Citrate tube instead of 3.2% Sodium Citrate tube
- Drawn in outdated/expired tube
- HCT > 55%
- Hemolyzed, icteric, or lipemic sample
Setup Schedule
Monday through Sunday, continuosly
Report Available
Daily
Reference Range
Refer to the Coagulation Reference Range document on this page - Downtime
For NOCO facilities, refer to the Coagulation Reference Range document found in the Resource section on the test list home page.
For NOCO facilities, refer to the Coagulation Reference Range document found in the Resource section on the test list home page.
Clinical Significance
Prolonged clotting times may be observed in the following situations: deficiency of Factors II, V, VIII, IX, X, XI, XII or fibrinogen, liver diseases, Vitamin K deficiency, presence of heparin, lupus anticoagulant or another inhibitor.
