APTT (Activated Partial Thromboplastin Time) Test

APTT test is neither a routine test nor a diagnostic test; it is used to check if further tests need to be done in a given condition. This test is performed along with other tests like prothrombin time (PT) when an individual shows the following symptoms:

• A clot in a vein or an artery
• Easy bleeding or bruising, which is sometimes unexplained (without any cause)
• Chronic liver disease (liver cirrhosis) that has caused poor blood clotting
• Acute episode of disseminated intravascular coagulation (DIC) that has caused an abnormal bleeding or clotting episode

APTT test is also performed in certain situations such as:

• Recurrent miscarriages: To detect the presence of auto-antibodies such as lupus anticoagulant antibody, which is associated with clotting episodes, and recurrent miscarriages.
• As a routine test: To monitor a patient on blood-thinning medications like heparin or when someone has switched from heparin to warfarin therapy; until the person is stabilized
• As a part of pre-operative profile: To screen for bleeding disorders

APTT test helps in evaluating the integrity of the intrinsic and common pathways of blood coagulation, while PT aids in evaluating the extrinsic pathway. Thus, in most cases, both these tests are performed simultaneously to avoid misdiagnosis.

No special preparations are needed for this test; however, a high-fat meal should be avoided prior to blood collection as high-fat levels in blood (lipemia) are known to alter test results.

It is a simple test in which a blood sample is collected from a vein in your arm by inserting a needle into the vein.

Normal results

The normal range for activated partial thromboplastin time is 25 to 35 seconds, which indicates the absence of bleeding or clotting issues and proper functioning of the intrinsic coagulation pathway.

Abnormal results

Abnormal results are categorized as prolonged (> 40 seconds), shortened (< 30 seconds) and critical levels (> 100 seconds). Prolonged and critical levels indicate bleeding issues, while shortened levels indicate clotting issues.

More than 40 seconds of APTT or prolonged APTT indicates:

• Congenital deficiency of clotting factors like factor VIII, IX, XI and XII, including hemophilia A and hemophilia B
• Congenital deficiency of prekallikrein
• Von Willebrand disease
• Liver cirrhosis or chronic liver disease
• Vitamin K deficiency
• DIC
• Heparin therapy

Less than 30 seconds of APTT or shortened APTT indicates:

• Early stage of DIC
• Extensive cancer
• A recent episode of acute hemorrhage

More than 100 seconds of APTT (critical level) indicates:

• Spontaneous bleeding
• Excessive drug therapy (heparin or warfarin therapy)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.