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Activated Partial Thromboplastin Time

420
4.2
NABL, ISO
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Overview
Interpretations
FAQ's
Activated Partial Thromboplastin Time

Overview of Activated Partial Thromboplastin Time

What is Activated Partial Thromboplastin Time?

The Activated Partial Thromboplastin Time (aPTT) Test measures the time taken by the blood to form a clot after the addition of substances (reagents) which activate the clot formation. The aPTT test is performed to detect a bleeding or clotting disorder and to monitor the treatment with anticoagulant medication (blood thinning medicine) like heparin.

Sample Type

The sample type collected for Activated Partial Thromboplastin Time is: Blood

Preparation for Activated Partial Thromboplastin Time

  • No special preparation required

Why Get Tested for Activated Partial Thromboplastin Time?

 

The Activated Partial Thromboplastin Time Test is performed:

·         To detect and diagnose bleeding or clotting disorder

·         Before performing a surgical procedure to assess the risk of bleeding

·         To monitor the treatment with blood-thinning medicines (e.g. unfractionated heparin therapy)

·         To investigate the cause of thrombotic episodes or recurrent miscarriages



Understand more about Activated Partial Thromboplastin Time

In case of any bleeding, the body responds to stop the blood loss as quickly as possible by forming a blood clot. This process of blood clotting or coagulation is called hemostasis and involves a series of chemical reactions in the blood (coagulation cascade) which activates blood proteins called coagulation factors one after another in a series. The activated coagulation factors lead to the formation of fibrin mesh around the platelets and other blood cells at the site of bleeding and this complex hardens to form a “blood clot”.

Coagulation cascade proceeds by two pathways, the intrinsic pathway, and the extrinsic pathway. These pathways later merge together into a common pathway. The Activated Partial Thromboplastin Time (aPTT) Test measures the functioning of Blood coagulation Factors I, II, V, XII, VIII, IX, X, and XI, along with other factors Prekallikrein (PK), and High Molecular Weight Kininogen (HK) which form parts of the intrinsic and common coagulation pathways.


The Activated Partial Thromboplastin Time (aPTT) Test measures the time taken by the blood to form a clot after the addition of substances (calcium and phospholipid emulsion) which activate clotting. The aPTT test result is compared to a control sample of normal blood.


The aPTT test is usually performed along with Prothrombin Time (PT) test to evaluate the cause of coagulation defect. PT test assesses the functioning of Blood Coagulation Factors I, II, V, VII, and X, which are parts of the extrinsic and common pathways by measuring the time taken for conversion of prothrombin to thrombin.



What Results of Activated Partial Thromboplastin Time mean?

Interpretations

Normal Reference Ranges:

Activated Partial Thromboplastin Time (aPTT):  30 - 40 seconds


In case the patient is receiving treatment with Heparin, the dose is adjusted so that the aPTT result is about 1.5 to 2.5 times the normal value.


Causes of prolonged aPTT are:

  • Inherited Coagulation factor deficiencies seen in conditions like von Willebrand disease, Hemophilia A and hemophilia B (Christmas disease) etc.

  • Acquired Coagulation factor deficiencies due to liver disease, deficiency of Vitamin K etc.

  • Presence of inhibitors, such as lupus anticoagulant and anticardiolipin antibodies, which bind to phospholipids present on the surface of platelets

  • Disseminated intravascular coagulation (DIC)

  • Leukemia


Causes of shortened aPTT are:

  • Disseminated intravascular coagulation (in Early Stages)

  • Extensive cancer (eg, ovarian, pancreatic, colon cancer)




The PT and aPTT tests are usually performed and evaluated simultaneously, and the results may be interpreted as follows:

PT RESULT

aPTT RESULT

CONDITIONS INDICATED

High

Normal

Liver diseases, Vitamin K deficiency, reduced activity of Factor VII, Disseminated Intravascular Coagulation (DIC), Warfarin treatment

Normal

High

Reduced activity of Factors VIII, IX, XI, or XII, von Willebrand disease, autoantibodies destroying one or more coagulation factors

High

High

Reduced activity of Factors I, II, V or X, liver diseases, DIC, an overdose of Warfarin

Normal

Normal

Normal hemostasis usually. However, normal results may also appear in a mild reduction in coagulation factor activity and mild cases of von Willebrand disease.




Patient Concerns about Activated Partial Thromboplastin Time

Frequently Asked Questions about Activated Partial Thromboplastin Time

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle attached is used to withdraw blood sample from a blood vessel in your arm generally from the inner side of the elbow area. The doctor, nurse or the phlebotomist will tie an elastic band around your arm which will help the blood vessels to swell with blood and hence makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You may feel a tiny pinprick during the procedure. Blood sample once collected is then sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, as this test involves a needle prick to withdraw the blood sample, rarely, a patient may experience increased bleeding, hematoma (blood collection under the skin) formation, bruising or infection at the site of needle prick.
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NABL

ISO

Sahyadri Speciality Labs is committed to provide the highest quality of Medical Laboratory services. There is a continual effort to ensure that the staff of the lab understands the Quality Policy & all the quality documentation, as well as follows the Quality manual and implements the Quality System Procedures all the time. By employing QMS, the lab strives to achieve the highest standard of service to provide the most reliable results, nearest to the true value and at most competitive rates. The lab is committed to good & ethical professional practices giving highest priority to client’s confidentiality and ensuring the reporting of the test values without any bias or influence. The lab implements the QMS so as to conform to ISO 15189:2007 and NABL 112 with the objective of Reducing reporting errors to the minimum, Minimizing customer complaints, Achieving maximum growth of the lab.
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