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Test Code APTT 1:1 APTT Mixing Study (APTT 1:1 Mix)

Important Note

Draw 1 tube- Must be completely filled.

If transport to the lab will exceed 4 hours: Immediately centrifuge the specimen and aliquot 2 mL of plasma into a separate plastic vial.  Send specimen frozen.

Performing Laboratory

Memorial Hospital Laboratory- Automated Procedures 304-388-5953

Specimen Requirements

Plasma- Light Blue Top, Sodium Citrate

Draw 1 full, tube by “clean” venipuncture (no excessive trauma).

Immediately after draw, invert tubes several times to mix blood with additive.

Specimen Rejection

  • Improperly labeled, collected, stored, and transported
  • Quantity not sufficient
  • Hemolyzed 
  • Marked lipemia 
  • Clotted specimens

When the mixing study is ordered, if the result of the undiluted PTT is within 5 seconds of the upper limit of normal, the mixing study will be cancelled.

Storage and Stability

Room temperature 18-24oC 4 hours
Frozen < -20oC 2 weeks
Frozen < -70oC 6 months

Reference Values

APTT and APTT heparin therauptic ranges may vary depending on specific lot number of reagent used in the laboratory.

Critical Value:

0-12 years old  > 60 seconds
>12 years old > 140 seconds

Methodology

Photometric Detection

Interpretation

Mixing studies are performed to help determine if the patient has a factor deficiency or a possible inhibitor.  Determination of the inhibitor may require incubation of the mixture at variable time intervals.

Days Test Set Up and Turnaround

Monday through Sunday, Continuously

AM Collection Expected by 9AM same day
Routine Expected within 24 hrs
Stat Expected within 1 hr
Timed Expected results are test dependant

CPT Coding

85732