Activated Partial Thromboplastin Time

Orderable EAP code:


Billable EAP Codes:

80001823 x 1

CPT Codes:

85730 x 1

Lab Section:

Core Lab

Turnaround Time:

Routine: 2 Hours
Urgent: 1 Hour

Test Schedule:

24 hours, 7 days a week.



Critical Values:

Greater than or equal to 200.0 seconds

Specimen Requirements:

3.2% sodium citrate tubes are acceptable provided they are filled to the line on the manufacturer's label. Tubes must be full (see comments below). Whole blood specimens are stable for 4 hours at room temperature. Whole blood specimens for monitoring heparin are stable for 1 hour at room temperature or 4 hours if plasma is separated from cells. Citrate plasma separated from cells is stable for up to 14 days at -20 degrees C.

Pediatric Specimen Requirements:

Add blood to the 1.3 mL mark of Pediatric BLUE top tube, 3.2% sodium citrate.

Reference Range:

Reference Range: 25.1 to 36.5 seconds
Therapeutic Range: 65 to 105 seconds (Heparin concentration of 0.30 to 0.70 U/mL).


APTT values for monitoring heparin therapy may be affected by specimens processed greater than 1 hour after collection.

Draw volume is critical due to the liquid anticoagulant. Allow tubes to fill by vacuum.

  • Tubes with rubber stopper: fill to line on label.
  • Tubes with plastic (Hemogard) cap: the fill level is above the top of the label.
  • Syringe: do not remove the vacutainer stopper. Insert the needle through the stopper and allow the tube to fill by vacuum. Do not overfill the vacutainer.
  • Pediatric tubes have no vacuum. Remove the cap and add blood to the 1.3 mL mark. Do not overfill.


Partial Thromboplastin Time