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
CPT Code:85730
Test Includes:
Turnaround Time:Performed and reported 24 hours/day.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens



Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - fill to fill line on tube
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - fill to fill line on tube
Collection Instructions:If the patient's hematocrit is >55%, contact laboratory to obtain a special tube.
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 tube; clotted specimen; refrigerated specimens, over-filled tubes.


Processing and Shipping

Specimen Processing:Send whole blood or platelet poor plasma. See Associated Link for additional processing instructions.
Shipping Instructions:Ship at room temperature. Whole blood specimens must arrive within 4 hours. If greater than 4 hours 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)


Interpretive

Critical Range:1 year and older: greater than 105 seconds
GICH: All ages - greater than or equal to 60.0 seconds
Reference Range:
0-30 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.
GICH: All ages - 29-50 seconds
Therapeutic Range:
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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