Laboratory Test Information Guide

Details for Partial Thromboplastin Time (Activated)- PTT

Test Name: Partial Thromboplastin Time (Activated)- PTT
Alternate Name(s): APTT
Laboratory: Core
Specimen Type: 2.7 mL Blue (3.2% Sodium Citrate) top Vacutainer

1.8 mL Blue (3.2% Sodium Citrate) top
*In cases where access is difficult, a 0.9 mL Blue top tube is acceptable
Collection Information: Tubes must be filled until vacuum exhausts (until the fill line marked on tube).
Both INR and PTT can be performed on one blue top tube. PTT analysis must be completed within 4 hours of collection.

Hemolysis affects PTT results and will not be reported on specimens with a high hemolysis grading as determined by the analyzer. For patients on cardiac bypass, ECMO or other ventricular assist devices, hemolyzed samples will have a reported PTT result.
Test Schedule: As required
Turnaround time from when specimen
is received in testing laboratory:
4 hours
1 hour
Reference Range: 0 min - 5 days: 31-54 seconds
5 days - 1 month: 25-60 seconds
1 month - 3 months: 32-55 seconds
3 month - 6 months: 29-50 seconds
6 months - Adult: 20-29 seconds

Therapeutic range for Heparin: 60-85 secs.
Effective Date: 2011-01-14
Revised Date: 2020-12-29
Critical Value: PTT: ≥100 (for patients NOT on anticoagulants)
Interpretive Comments: Detects abnormalities in the Intrinsic pathway. Useful in monitoring heparin therapy.
Special Processing:  
Method of Analysis: Optical clot detection
Critical Information Required:  
Storage & Shipment: Blue (Sodium Citrate) top specimens are kept at 18-24 degrees Celsius.

Samples from patients on therapeutic heparin must be centrifuged within one hour of collection and tested within four hours.

All other samples should be centrifuged and tested within 4 hours of specimen collection.

Samples are discarded after 24 hours.
System Codes: 
Referred To:  

Questions? Comments? Contact Laura Gopaul