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Test Code TT THROMBIN TIME [LAB324]

Performing Laboratory

Pathology Laboratory Des Moines, IA

Clinical Testing | Pathology Laboratory

Laboratory Section: 

Core Laboratory

 

Test Performance

Performed: 

Daily, 24 hours

Specimen Requirements

Container/Tube Type: 

Light Blue (Citrate)

 

Collection Information: 

Collect one full blue top tube

 

Transport Information: 

  1. Spin down, remove plasma, spin plasma again, and place 1 mL of platelet-poor plasma in plastic vial. (Glass vial is not acceptable.) Note: Double-centrifuged specimens are critical for accurate results as platelet contamination may cause spurious results. 
  2. Freeze specimen immediately at ≤ -40° C, if possible.
  3. Send specimen frozen.

Note: Each coagulation assay requested should have its own vial.
 

 

Minimum Sample Volume: 

0.5 mL of plasma (approximately 1.0 mL of whole blood based upon a normal patient's hematocrit)

 

Unacceptable Conditions: 

Hemolyzed or lipemic specimens.

Specimen Stability

Platelet Poor Plasma
Centrifuge Specimen
Recommended centrifuge speed is 1500 x G for at least 15 minutes. Be careful that the tubes are evenly balanced when placing them into the centrifuge. When the centrifuge stops, carefully remove and rack tubes. Be aware that an unbalanced centrifugation, speed too slow, or centrifugation for too short of a spin time may all lead to an increase number of cells in the plasma which could contribute to a clotted specimen or erroneous results.
Remove Plasma
To remove plasma, start from the top, gently draw specimen into pipette as you go further down tube. Leaving approximately 0.5mL of plasma will insure that you do not disturb the buffy coat and cell layer.
Second Spin
Plasma separated from cells goes back into the centrifuge for a second spin. Balance and centrifuge the tubes. Failure to perform a second spin will result in plasma containing too many platelets which interfere with some coagulation testing and is a contributing factor for a clotted specimen.
Transfer Plasma to Aliquot Tubes
Pipette plasma from second spin tube into labeled aliquot tubes without disturbing the bottom 0.5mL.
Specimen Storage
Promptly freeze specimens after processing.

Refrigerated Stability: 

NOT Acceptable

 

Frozen Stability: 

30 days

 

Ambient Stability: 

2 hours

CPT Code

85670

Methodology

Clot-Based Assay