Partial Thromboplastin Time (PTT)

Sunquest Code:PTT  
Epic Code:LAB56Epic Name:Partial Thromboplastin Time (PTT)
Synonyms:APTT; Activated Partial Thromboplastin Time
Methodology:Electromagnetic clot detection
Test Includes:
Turnaround Time:Performed and reported 24 hours/day.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens

Collection Instructions

Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on tube
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on tube
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Collection Instructions:If the patient's hematocrit is >55%, contact laboratory to obtain a special tube. If using a butterfly needle, a waste tube must be collected before the blue top.
After Care:If the patient has a coagulation abnormality, apply direct pressure to the puncture site for 10 minutes; apply a pressure dressing. Instruct the patient to leave the bandage on for 12 hours.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, specimens collected in 3.8% buffered citrate.
Grand Itasca: Whole blood specimen greater than 4 hours old or not processed appropriately within 1 hour of collection.
All other Fairview sites: Specimen greater than 2 hours old or not processed appropriately within 1 hour of collection.

Processing and Shipping

Specimen Processing:Send whole blood or platelet poor plasma. See Associated Link for additional processing instructions.
Shipping Instructions:Ship whole blood specimens at room temperature.
  • Grand Itasca: Whole blood must be processed within 1 hour; processed specimen can be stored unopened at room temperature for up to 4 hours. If >4 hours, aliquot off and freeze at -20°C for up to 2 weeks, or -70°C for up to 6 months.
  • All other Fairview sites: Whole blood specimens must be processed within 1 hour of collection and tested within 2 hours. If greater than 1 hour is required for transport, follow specimen processing instructions and ship frozen plasma on dry ice.
Test Performed at or Referral Lab Coagulation  (University of Minnesota Health Maple Grove Clinics, Fairview Range - FRMC, UMMC-East Bank, Oxboro Bloom, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Northland - FNMC, Fairview Southdale - FSH, UMMC/UMMCH-West Bank, M Health Clinic and Surgery Center, Grand Itasca GICH)


Critical Range:Greater than 105 seconds
Grand Itasca (GICH): All ages - greater than or equal to 60.0 seconds
Reference Range:
Grand Itasca (GICH): 22-37 seconds (all ages)
All other Fairview sites:
0-29 days 27-52 seconds
1-5 months 24-47 seconds
6 months and older 22-37 seconds
PTT on premature infants are approximately 20% higher. 
Therapeutic Range:
All Fairview sites, excluding Grand Itasca (GICH).

The target aPTT range for heparin therapy is:
  • High dose protocol (for deep vein thrombosis and pulmonary embolism): 60-101 seconds
  • Low dose protocol (for AMI, post-thrombolytics, unstable angina, prosthetic valve): 48-65 seconds

Target range for anticoagulation with direct thrombin inhibitors, e.g., lepirudin [Refludan, bicalirudin, argatroban] is approximately 1.5-2.5 times the baseline aPTT.    
Use: Monitoring heparin therapy; evaluation of intrinsic coagulation system. Aid in screening for the following: classical hemophilia (A and B); Christmas disease; congenital deficiencies (factors 2, 5, 8, 9, 10, 11, and 12; Fitzgerald factor; vitamin K; prekallikrein; hypofibrinogenemia); disseminated intravascular coagulation; liver failure; circulatory anticoagulant.

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