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Specimen Requirements


Preferred: Full blue-top (sodium citrate) 1.8 mL tube-Hemolyzed or short draw specimen is not acceptable.
Specimen Volume:
 0.5 mL sodium citrate plasma

Stability: Centrifuged specimens at 2-4°C or at 18-24°C must be tested within 4 hours of specimen collection.

Collection Instructions: Centrifuge immediately after draw. Forward promptly. If there is a delay in transport of >4 hours or if mailing time exceeds 4 hours, spin down, remove plasma from cells and freeze immediately in plastic vial. Send specimen frozen. Specimen stability is ≤2 weeks when frozen at -20° C.


NOTE:  Patients with a hematocrit of >55% must be recollected using an altered amount of sodium citrate.

Reference Values

Refer to PTT for reference ranges.


Performing Laboratory

St. Luke's Hospital Cedar Rapids

Day(s) Test Set Up

Monday through Sunday

Useful For

For patients in the NICU, heparin is used to flush and keep the umbilical lines patent.  Even with the withdrawal of waste, heparin may remain in the line.  The sample treated with Hepzyme rules out heparin contamination being responsible for abnormal coagulation results.


Clot Based Assay

Testing Classification and CPT Coding