Partial Thromboplastin Time, Activated (aPTT)

CPT Code(s):

  • 85730

Preferred Specimen:

One full 3.2% unopened sodium citrate (light blue-top) tube

Minimum Volume:

Ratio of blood to citrate is critical. Submit difficult draws in a pediatric (light blue-top) tube. 0.5 mL frozen plasma.

Alternate Specimen:

1 mL frozen plasma: for Heparinized patients or if testing will be delayed longer than 6 hours, centrifuge specimen within 1 hour of collection at 2500-3500 rpm. Transfer plasma to a plastic screw-cap vial and freeze at -20¡C immediately. Ship with dry ice.

Special Instructions:

Correct ratio of blood to citrate is critical. Do not overfill or under fill collection tube. Mix by inversion 4 times. For non-heparinized patients, maintain specimen at room temperature. Do not uncap. Stable 24 hours at room temperature.

Transport Container:

3.2% sodium citrate (light blue-top) tube

Transport Temperature Name:

Room temperature

Specimen Stability Components:

  • Room Temperature: Unopened light blue-top tube Room temperature: 24 hours Frozen: Unacceptable Separated platelet poor plasma Frozen -20¡C: 7 days

Testing Schedule:



Mechanical Clot Detection

Reference Range:

Reagent Lot Specific (30-40 sec)

Reject Criteria:

Gross hemolysis ¥ Gross lipemia ¥ Improper blood to citrate ratio ¥ Clotted ¥ High hematocrits

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