Activated Partial Thromboplastin Time (APTT)

 Activated partial thromboplastin time (APTT) evaluates the function of the contact activation pathway and coagulation sequence by measuring the amount of time it requires for recalcified citrated plasma to clot after partial thromboplastin is added to it. The test screens for deficiencies and inhibitors of all factors, except factors VII and XIII.

Normal lab value for activated partial thromboplastin time:

• 20 to 60 seconds, depending on the type of activator used.

Indication for APTT: 

• Monitors the effectiveness of heparin therapy.
• Detect coagulation disorders in clotting factors such as hemophilia A (factor VIII) and hemophilia B (factor IX).
• Determine individuals who may be prone to bleeding during invasive procedures.

Nursing consideration for APTT: 

• Do not draw samples from an arm into which heparin is infusing.
• If the client is receiving intermittent heparin by intermittent injection, plan to draw the blood sample 1 hour before the next dose of heparin.
• Apply direct pressure to the venipuncture site.
• Blood specimen should be transported to the laboratory immediately.
• The aPTT should be between 1.5 and 2.5 times normal when the client is receiving heparin therapy.
• Monitor for signs of bleeding if the aPTT value is longer than 90 seconds in a patient receiving heparin therapy.