Prothrombin Time and Activated Thromboplastin Time Panel

Test Code
PT(LOW ISI) AND PTT


Alias/See Also
Prothrombin Time
Activated Partial Thromboplastin Time
Hematology


Includes
Prothrombin Time
INR
Activated Thromboplastin Time


Preferred Specimen
Light Blue Top Tube – 3.2% sodium citrate


Transport Temperature
Room temp. Do not place directly on ice.


Specimen Stability
Whole blood, unopened tube, centrifuged or uncentrifuged
PT(LOW ISI):
24 hours stability from time of collection in an unopened tube at room temperature. Storage at refrigerated temps may result in cold activation of factor VII, so any blue tops received in ice may be rejected.

PTT:
Whole Blood
Non-heparinized patients (or patients on heparin that is not unfractionated heparin)
 Room temperature/Refrigerated: 6 hours

Patients on unfractionated heparin – deliver to the laboratory ASAP

Room temperature: 1 hour
Patients on direct oral anticoagulants
 Room temperature: 2 hours


Aliquoted Plasma
Non-heparinized patients (or patients on heparin that is not unfractionated heparin)
 Room temperature: 6 hours
Frozen: 3 months at -20C or 4 months at-70C.
Patients on unfractionated heparin – deliver to the laboratory ASAP
Room temperature: 1 hour


Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Under drawn or overdrawn, clotted and hemolyzed specimens are not acceptable for testing. Patient's receiving anticoagulant therapy may give spurious results.
 


Methodology
Photo-optical endpoint

Setup Schedule
Daily


Report Available
TAT 1 day


Limitations
Monitor warfarin patients based on the INR value only!
INR therapeutic range for patients on oral anticoagulant therapy is 2.0-3.5.
For patients who are not receiving anticoagulant therapy, the INR of 1.1 or lower is considered normal.


Reference Range
Test Reference range Units
PT 9.8 - 13.3 Sec
INR ≤1.1  
PTT 27.9 - 37.0 Sec
Heparinized PTT 55 - 94 (Therapeutic) Sec

Comments:
  1. For normal patient who are not on anticoagulation, the INR of 1.1 or lower is considered normal.
  2. Therapeutic range for patients on anticoagulant should be between 2.0-3.5

 


Performing Laboratory
Test performed in BACL Hematology Labs
Contact West Roxbury: Nolan Raymond 857-203-5980
Alternate contact   Joseph A. Manzone JP 857-364-5092
Alternate contact Diane Robert  Brockton 774-826-2294
Alternate contact Bhumikaben Patel Bedford 781-687-2976


Last Updated: September 19, 2025


The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.