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Test Code MIXSDY Mixing Studies (Coagulation Inhibitors), Blood, LAB2614


Clot Based Assay

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred:  3 Full blue-top (sodium citrate) 1.8mL tube-Hemolyzed or short draw specimen is not acceptable.
Specimen: minimum volume: 2.0mL plasma

Stability: Centrifuged specimens at 18-20°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 >2 hours but ≤8 hours, spin down, remove plasma from cells and send specimen refrigerated. Specimen separated from cells and stored at refrigerate temperature is stable for ≤4 hours.  If testing not performed within 4 hours, plasma should be removed from cells and frozen at -20°C for 2 weeks.

NOTE: Patient cannot be on heparin or Coumadin.

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




Reference Values

PT: 10.8-13.0 seconds
APTT: 25.0-34.5 seconds
Correction of prolonged PT and/or APTT values after mixing 1:1 with normal plasma

Critical Values:
PT: >30.0 seconds
APTT: >50.0 seconds

Day(s) Test Set Up

Monday through Friday (days only)

Test Classification and CPT Coding

85611-PT mix
85732-APTT mix

Useful For

The presence of acquired circulating anti-coagulants is commonly associated with certain disease entities, ingestion of drugs, and other clinical situations.  Acquired inhibitors can occur in patients with non-congenital deficiencies.