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Activated Partial Thromboplastin Time
MessageCoagulation
Test Code
LAB325
Alias/See Also
APTT, PTT
CPT Codes
85730
Preferred Specimen
2.7 ml whole blood (blue top tube, citrate) TUBE MUST BE FULL
Minimum Volume
2.7 mL whole blood filled to the designated line on specimen container (blue top tube, citrate)
Other Acceptable Specimens
1.8mL Low Volume blue top tube, citrated
Instructions
APTT: testing must be completed within 4 hours of collection.
LAB: Centrifuge in validated Platelet Poor Plasma Centrifuges only
LAB: Centrifuge in validated Platelet Poor Plasma Centrifuges only
Transport Container
Processed Platelet Poor Plasma, preferably frozen
Transport Temperature
Processed Platelet Poor Plasma:
Room Temp – 4 hours
Refrigerated – 4 hours
Frozen – 2 weeks
Room Temp – 4 hours
Refrigerated – 4 hours
Frozen – 2 weeks
Specimen Stability
Whole Blood: Ambient 4 hours
Plasma separated from whole blood 2-8°C 4 hours
Plasma separated from whole blood -20°C 2 weeks
Plasma separated from whole blood -70°C 6 months
Plasma separated from whole blood 2-8°C 4 hours
Plasma separated from whole blood -20°C 2 weeks
Plasma separated from whole blood -70°C 6 months
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Underfilled tube - Quantity not Sufficient (QNS)
Clotted specimen
Clotted specimen
Methodology
The activated partial thromboplastin time (aPTT) is a screening procedure for deficiencies in intrinsic coagulation Factors II, V, VIII, IX, X, XI, XII, aPTT substitution test, and the monitoring of heparin therapy. A plasma sample is incubated with an optimal quantity of phospholipids and a negatively charged contact activator which initiates the activation of the intrinsic coagulation pathway. Calcium is added after incubating at 37°C for a specific period of time, and the time for clot formation is measured. The aPTT is reported as time in seconds.
Report Available
Same Day
Limitations
Hemoglobin up to 500 mg/dL
Bilirubin up to 26 mg/dL
Triglycerides up to 1000 mg/dL
Bilirubin up to 26 mg/dL
Triglycerides up to 1000 mg/dL
Reference Range
APTT: 25 - 37 seconds
Critical Value >125 seconds
Critical Value >125 seconds
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 other inhibitor.
Performing Laboratory
HHN/HHI