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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 -20oC
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 -20oC
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- Drawn in outdated/expired tube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
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.
