ACTIVATED PARTIAL THROMBOPLASTIN TIME

• Tube MUST be full for proper whole blood to anticoagulant ratio.  See Additional Information below.
• Platelet-poor plasma preferred; see Additional Information below for instruction.
• If a butterfly needle is used for collection, a NON-ADDITIVE discard tube must be drawn first.
• Whole blood specimen stability may be adversely affected by heparin therapy, labile clotting factors, and hepatic function.
• It is preferred that samples are centrifuged, aliquoted, and frozen.  See Obtaining A Platelet-Poor Sample below.

Centrifuge and remove platelet-poor plasma if testing will be delayed > 1hour from collection.  If not tested within 4 hours of collection, freeze plasma.  See Obtaining A Platelet-Poor Sample below.

PT and PTT can be performed on a single blue top tube. If ordered together, the preferred sample handling is to centrifuge and aliquot platelet-poor plasma into a transfer tube then freeze.
Whole blood maintained at room temperature will be accepted for non-therapeutic patients only.

If blood is drawn from an indwelling catheter, the line should be flushed with saline and the first 5 mL of blood discarded.

• Plasma samples must be frozen.
• Whole blood samples must be submitted at room temperature. (Non-therapy Patients only)
• Do not freeze or refrigerate whole blood.

• -20ºC (frozen) plasma samples are stable up to 14 days
• Non-therapy Patients:  15-25ºC (room temperature) whole blood up to 24 hours

The following criteria will result in a rejection:

• Hemolyzed sample
• Clotted sample
• Sample tube underfilled or overfilled
• Whole blood submitted refrigerated or frozen

Non-therapeutic Range:    25.0 - 36.0 seconds

APTT Therapeutic Range: 65.0 - 90.0 seconds. 

Coag screen for plasma-clotting factors, not factors VII and XIII; screen for defects of the extrinsic and common coagulation pathways. If blood is drawn from an indwelling catheter, the line should be flushed with saline and the first 5ml of blood discarded.