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Order Code LAB2602 Activated Partial Thromboplastin Time (aPTT), Blood

Useful For

PTT is useful as a coagulation screening test for coagulopathy.

Specimen Requirements

Draw a full, light blue-top (sodium citrate) tube. For pediatric (minimum ) volume use the 1.8 mL tube.  Allow tube to fill completely. Invert gently several times to mix blood.  If collected offsite, please send frozen platelet-poor plasma.

Specimen Stability

Specimen Type Temperature   Stability                 
Whole Blood Ambient 4 hours
Platelet Poor Plasma (See below) Frozen 2 weeks

Platelet Poor Plasma Instructions:

  1. Centrifuge the primary tube within four hours of draw
  2. Transfer plasma to an aliquot tube
  3. Centrifuge the aliquot tube
  4. Transfer plasma to a second aliquot tube
  5. Freeze the second aliquot tube

Rejection Criteria

  1. Specimens that are clotted
  2. Visible hemolysis
  3. Tube volume below minimum fill line (<90% expected fill) or above maximum fill line

Reference Values

  • 25.1 - 36.5 seconds
  • Critical value (automatic call-back): > 120 seconds
     

The therapeutic APTT range in seconds should correspond with the Unfractionated Heparin (UFH) concentration of 0.3-0.7 U/mL as assessed by a heparin assay (inhibition of factor Xa activity with detection by chromogenic substrate). We have established the therapeutic APTT range to be approximately 60-95 seconds. This therapeutic heparin curve has been established for an individual that has been using a factor X inhibitor and is being anticoagulated with UFH. This curve should not be used to monitor UFH alone; a Heparin Anti Xa assay is the preferred method. 

Day(s) Test Set Up

Monday through Sunday

Performing Laboratory

Ridgeview Medical Center Laboratory

Two Twelve Medical Center Laboratory

Ridgeview Sibley Medical Center Laboratory

Ridgeview Le Sueur Medical Center Laboratory

Methodology

Photo-Optical Clot Detection

Test Classification and CPT Coding

85730