Activated Partial Thromboplastin Time

Message

Coagulation

Test Code

LAB325

Alias/See Also

Activated Prothombin Time, APTT, PTT

CPT Codes
85730

Preferred Specimen

Blue top 3.2% citrated tube, plasma
Note: Do NOT place blue top tube on ice

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 (microtainer)

Instructions

LAB: Centrifuge in validated Platelet Poor Plasma Centrifuge for 2 minutes at 7200 rpm. Specimen to be delivered to Coagulation department STAT. Notify CLS upon arrival.
**Testing must be completed within 4 hours of collection.

Note: If unable to deliver whole blood to testing laboratory within stability time, platelet poor plasma should be aliquoted and placed in freezer. Centrifuge light blue-top for 2 minutes at 7200 rpm (STAT Coag centrifuge) 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 aliquoted plasma a second time and transfer platelet-poor plasma into a new plastic vial and place in 2 – 8℃ refrigerator or freeze -20℃ if delay longer than 1 hour. Once thawed, specimen must be tested within 2 hours.

Freeze aliquot at -20℃ for at least 1 hour when sending to alternate campus for testing.

Transport Container

Ambient: whole blood 4 hours
Frozen (-20℃): plasma frozen for at least 1 – 2 hours

Transport Temperature

Hemolyzed, clotted specimen, contaminated, underfilled tube - Quantity not Sufficient (QNS), overfilled tube, whole blood specimen transported on ice

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

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Underfilled tube - Quantity not Sufficient (QNS)
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.

Setup Schedule

Everyday

Report Available

Same Day

Limitations

Hemoglobin up to 500 mg/dL
Bilirubin up to 26 mg/dL
Triglycerides up to 1000 mg/dL

Reference Range

APTT: 25 - 37 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

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.