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Test Code PTT Activated Partial Thromboplastin Time (APTT)  [LAB325]

Test Method

Mechanical Clot Detection; Diagnostica Stago

Performance

Testing is performed Monday through Sunday.

Routine orders: Typically completed within 4 hours upon receipt in the lab.

STAT orders: Typically completed within 25 minutes upon receipt in the lab.

Specimen Requirement

  1. Sodium citrate blue-top tube filled to the area within the indicator arrow printed on the side of the tube.
    Important: Underfilled and overfilled tubes will be rejected.
  2. Transport tube to the lab as soon as possible. Tubes should be spun within one hour of collection and tested within 8 hours for unheparinized patients and 4 hours for patients on unfractionated heparin.
  3. If the specimen cannot be sent to the lab immediately, spin down and remove plasma from the cells and freeze to at least -20C. The specimen must then remain frozen during transport to the lab.
  4. Blood collection using a butterfly needle is not recommended. If using a winged butterfly setup, collect a "discard tube" first to account for the dead space in the butterfly tubing. 
  5. Do not "force fill" into a vacutainer tube.
  6. Do not remove the cap of a blue top citrate tube.

Useful For

Monitoring heparin therapy (unfractionated heparin [UFH]).

Screening for certain coagulation factor deficiencies.

Detection of coagulation inhibitors such as lupus anticoagulant,
specific factor inhibitors, and nonspecific inhibitors. 

Reference Values

22-34 Seconds for Non-anticoagulated samples

  • Critical Value: > 150 Seconds

Therapeutic Range: 61-107 Seconds

Since activated partial thromboplastin time (APTT) reagents can vary greatly in their sensitivity to
unfractionated heparin (UFH), it is important for laboratories to establish a relationship between APTT response and heparin concentration. The therapeutic APTT range in seconds should correspond with an UFH concentration of 0.2 to 0.4 U/mL as assessed by heparin response curve. In our laboratory, we have found the therapeutic APTT range to be approximately xx to xx seconds.

CPT Code Information

85730 Coagulopathy Testing: Thromboplastin
time, partial (PTT); plasma or whole blood