• Tube MUST be full for proper whole blood to anticoagulant ratio.  See Additional Information below.
  • 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.

Test Code

Alias/See Also

CPT Codes

Preferred Specimen
1 Blue tube (Sodium Citrate)

Minimum Volume
0.5 mL plasma

Other Acceptable Specimens
Whole blood samples will be accepted maintained at room temperature


The preferred sample: Centrifuge and remove platelet-poor plasma then freeze.  See Obtaining A Platelet-Poor Sample below.
Alternate: Blue top whole blood sample maintained at ROOM TEMPERATURE will be accepted. See stability 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.

Transport Temperature
  • Plasma samples must be frozen.
  • Whole blood samples must be submitted at room temperature.
  • Do not freeze or refrigerate whole blood.

Specimen Stability
  • 15-25ºC (room temperature) whole blood up to 24 hours
  • -20ºC (frozen) plasma samples are stable

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

The following criteria will result in a rejection:

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

Photo-Optical Clot Detection

Setup Schedule
M, T, W, Th, F, Sa, Sun

Report Available
Same day tested.

Reference Range

25.0 - 36.0 seconds

Clinical Significance

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.

Performed By
Alverno Laboratories

Performing Laboratory
Alverno Central Lab  
NHMC (Hematology, IL Coag)

Additional Information
BD Vacutainer Plus Blue Top Volume Fill Guide
Obtaining A Platelet-Poor Sample

Last Updated: June 6, 2023

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.