Prothrombin with INR and Partial Thromboplastin Times Test
This test measures PT/INR and activated partial thromboplastin time (aPTT) from a blood sample. Quest describes these as screening measurements for coagulation factor abnormalities, used to monitor warfarin therapy and to study clotting disorders.
About this test
PT/INR reflects coagulation factors in what is called the extrinsic pathway of clotting. aPTT reflects factors in the intrinsic pathway (factors VIII, IX, XI and XII) and the common pathway (factors II, V, X and fibrinogen), and is used to screen for deficiencies or inhibitors affecting those factors.
Quest lists these measurements as used to screen for coagulation factor abnormalities, to monitor the effect of warfarin therapy, and to study people with hereditary or acquired clotting disorders.
Who might consider this test?
- The two measurements are read together, since each reflects a different part of the clotting pathway.
Test details
| Collection | Quest patient service center |
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Quest resources
Additional details
What this test looks at
The test reports three values: INR, PT and activated partial thromboplastin time. Quest also lists this combination under the names PT, PTT and aPTT, reflecting the individual measurements that make up the panel.
This test isn't part of the Celio Health store at the moment, so it can't be ordered or requested here. The test menu lists everything that can.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does this test measure?
It measures PT, INR and activated partial thromboplastin time (aPTT), reflecting different parts of the blood clotting pathway.
How is the sample collected?
The sample is a blood specimen collected in a sodium citrate (light blue-top) tube.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
What is this test used for?
Quest lists it as used to screen for coagulation factor abnormalities, to monitor the effect of warfarin therapy, and to study hereditary and acquired clotting disorders.