Test Code PTT Activated Partial Thromboplastin Time (APTT) LAB325
Test Method
Clot Based Assay; ACL Systems
Specimen Requirement
Sodium citrate blue-top tube filled to the area within the
indicator arrow printed on the side of the tube.
Additional Specimen Collection Information
Invert the sodium citrate tube end to end 4 times to
thoroughly mix blood and anticoagulant. The tube should be left
stoppered until time of testing. Specimens stored at room
temperature should be centrifuged and tested within four hours
of
specimen collection.
Precautions:
- It is not recommended to use a winged
blood
collection set (Butterfly). - If a vacuum tube butterfly must be used, the first tube in
the
series will be under-filled. Collect a “discard citrate
tube”, and then collect the citrate tube used for testing.
This will ensure the proper blood to anticoagulant ratio. - If using a syringe, use a BD Blood Transfer Device to
transfer
blood from the syringe to the citrate tube within one minute of
collection. Hold the syringe with the plunger in the up-right
position and allow the vacuum present to fill the tube. Before
collection, be sure the syringe plunger is pushed to the top of the
syringe. The transfer device may pop up and needs to be
held down to completely fill tube to between fill
lines. - Do not “force fill” blood into a vacuum tube.
This
may result in activation of the platelets possibly leading to
erroneous results. Allow the vacuum present to fill the tube. - Do not remove vacuum tube cap to add blood.
- Specimens should be obtained from a single venipuncture
with
minimal tissue trauma. Never combine multiple blood collections
into a single vacuum tube. - Never re-use a syringe that was used for a pic line saline
flush.
Refer to the “Citrated Plasma for Coagulation
Studies” protocol
in the Quality Assurance Manual.
Reference Values
25-37 Seconds for Non-anticoagulated samples
-
Critical Value: > 100 Seconds
Therapeutic Range: 44-74 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 44 to 74 seconds.
Performance
Testing is performed Monday through Sunday.
Routine orders: Typically completed within 4 hours.
Expedite orders: Typically completed within 1 hour after the
specimen arrives at the testing site.
STAT orders: Typically completed within 25 minutes after the
specimen arrives at the testing site.
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.
LOINC Code Information
14979-9 Activated Partial Thromboplastin Time (aPTT) In
Platelet
Poor Plasma By Coagulation Assay
CPT Code Information
85730 Coagulopathy Testing: Thromboplastin
time, partial (PTT); plasma or whole blood