What it means
A clotting test that checks the intrinsic and common pathways of coagulation. It is used to watch IV unfractionated heparinHEP-uh-rinAn anticoagulant drug, given by injection or IV, that keeps blood clots from forming or growing.Full entry therapy and to look for bleeding disorders such as hemophilia. A longer time means blood takes longer to clot. The older partial thromboplastin time (PTT) test measures the same thing, and the two names are often used interchangeably.
For the nurse
Check the result before changing a heparin drip rate, following the facility's heparin protocol. With a high value, watch for bleeding: gums, urine, stool, bruising and IV sites. Protamine sulfate reverses heparin.
At a glance
| Normal range | About 30–40 seconds; each lab sets its own range. During heparin therapy the goal is often 1.5 to 2.5 times the control value. |
|---|---|
| Critical range | Above about 70 seconds in many labs; each lab sets its own critical values. |
| Abbreviations | aPTT; PTT |
| Spanish | tiempo de tromboplastina parcial activada |
| Also written | aPTT, partial thromboplastin time, PTT |
Related terms
platelet
A tiny cell fragment in the blood that sticks together at a wound to help form a clot.
anticoagulant
A drug that slows the blood's ability to form clots.
heparin
An anticoagulant drug, given by injection or IV, that keeps blood clots from forming or growing.
blood clot
A soft, gel-like clump that forms when blood changes from a liquid to a solid.