WHAT IS ACTIVATED PARTIAL THROMBOPLASTIN TIME?
THROMBOPLASTIN:
WHY IS APTT TEST PERFORMED?
APTT test is performed for the following reasons:
- To investigate unexplained bleeding
- To check for clotting disorders
- To help investigate recurrent miscarriages
- To help diagnose antiphospholipid syndrome (APS)
- If a person is on blood-thinning medicines, the doctor will ask for a PT or INR test, to rule out the effectiveness of the medicine
- Before any surgical procedure
WHAT DOES THE TEST MEASURE?
The Activated Thromboplastin Time (APTT) test measures the ability of the blood to clot to detect a bleeding or clotting disorder.
APTT is ordered regularly if a patient is on anticoagulant drugs. This test is also ordered on patients, who are not on anticoagulant drugs but has signs and symptoms of excessive bleeding or clotting, such as
- Unexplained bleeding
- Easy bruising
- Bleeding gums
- Nosebleeds
- Acute or chronic conditions
Q1) How is the test performed?
This test is performed on a blood sample. The blood is obtained from the vein and this is performed by a health care provider in the following way.
- clean the skin
- put an elastic band above the area
- insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand)
- pull the blood sample into a vial or syringe
- take off the elastic band and remove the needle from the vein
Q2) What are the risks associated with this test?
Very few risks are associated with having blood drawn for an APTT test. However, if you have a bleeding disorder, you are at a slightly higher risk for excessive bleeding and hematoma (blood that accumulates under the skin).
There is a very small risk of infection at the puncture site. You may feel slightly faint or feel some soreness or pain at the site where your blood was drawn.
Q3) Any preparation required before the test?
Inform your doctor if you are on any medication, that can affect clotting time.
Q3) What additional tests are performed in case of abnormal partial thromboplastin time?
Additional tests that are prescribed in case of abnormal partial thromboplastin time are:
- Prothrombin time (PT)
- Liver function test (LFT)
- Platelet count
- Complete blood count (CBC)
- Fibrinogen test
- Coagulation factor test
INTERPRETATION OF THE TEST RESULTS:
A prolonged APTT means that clotting is taking longer to occur than normal and may be due to a variety of causes.
A prolonged APTT may be due to:
Underlying conditions that cause low levels of clotting factors, such as:
- Liver disease
- Vitamin K deficiency: vitamin K is essential for the formation of several clotting factors. Vitamin K deficiencies are rare but can be caused by an extremely poor diet, malabsorption disorders, or prolonged use of certain antibiotics, for example. PT is more likely to be prolonged than is PTT.