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Test Code BLOD0673 Partial Thromboplastin Time Activated (APTT)

Useful For

  • A screening test for the intrinsic coagulation system
  • Testing relative heparin activity in heparinized patients

Methodology

Photometric Detection

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

Specimen must arrive and be tested within 4 hours of draw.

 

Specimen Type: Whole blood
Container/Tube: Blue top (3.2% sodium citrate)

Specimen Volume: Full tube

Collection Instructions: Click here to link to a You Tube video tutorial

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

2. Send specimen in original tube.

3. If there is a delay in transport of >4 hours, specimen must be double-centrifuged to prepare a platelet-free plasma specimen as follows:

a. Immediately centrifuge at 3,200 rpm for 15 minutes.

b. Carefully remove plasma from cells avoiding platelet/buffy coat, and transfer plasma into a plastic tube.

c. Centrifuge plastic tube at 3,200 rpm for 15 minutes.

d. Carefully remove top portion of plasma and transfer plasma into a plastic tube leaving approximately 250 mcL in bottom to discard.

e. Double-centrifuged plasma should be aliquoted (0.5 mL-1 mL each) into clearly labeled plastic tubes. (Glass vial is not acceptable.)

Note: Number of tests ordered will determine number of aliquots needed, generally 1 aliquot per test.

f. Specimens should be frozen at <-40° C, if possible, and sent together in same container with at least 5 lbs of dry ice. Specimens must arrive in a frozen state.

Additional Information: Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

Specimen Transport Temperature

Whole blood Ambient <4 hours/Plasma Frozen >4 hours

Specimen Stability

Specimen Type Temperature Time
Whole Blood (unspun) Ambient 4 hours
Plasma Na Citrate (double spun) Frozen 14 days

 

Reference Values

24.5-34.0 seconds

 

Critical value (automatic call-back): >100 seconds

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

85730