Definition

APTT (Activated Partial Thromboplastin Time) is a blood clotting test that measures the time, in seconds, it takes for blood to clot. Typically, when a blood vessel is injured or bleeding occurs, the body will form a clot within a specific timeframe to prevent excessive blood loss.

This clotting process involves proteins that signal blood clotting factors to create clots at the site of injury or bleeding. The activation of these clotting factors requires time; any disruption in their formation can lead to prolonged bleeding and significant blood loss.

The body contains multiple blood clotting factors. If any of these factors are not produced adequately, the clotting process may be impaired, resulting in slower and prolonged clotting times. Therefore, the APTT test assesses the functionality of these clotting factors.

The APTT test is crucial in diagnosing various blood clotting disorders in both children and adults. For example, in children, it can aid in the early detection and diagnosis of hemophilia. Furthermore, in adult patients receiving anticoagulant therapy, the APTT test is used to monitor their treatment.

Individuals with a family history of blood clotting disorders are encouraged to undergo APTT testing for early detection, particularly in children, to prevent life-threatening bleeding events. While APTT testing cannot specifically diagnose blood clotting disorders, it can indicate potential dysfunction in clotting factors, necessitating further examinations such as the PT (Prothrombin Time) test.

Indications

The APTT test is applicable in various conditions and purposes, including:

• Symptoms of spontaneous bleeding or unexplained bruising on the skin
• Easily bleeding gums
• Frequent nosebleeds
• Wounds that do not stop bleeding
• Pain and swelling in joints
• Presence of blood in urine and stool
• Extended menstruation with heavier blood loss than usual in women

Additionally, the APTT test is used for pre-surgical screening and to monitor blood clotting factors during anticoagulant therapy.

Contraindications

There are no contraindications for the APTT test. However, several medications, supplements, and vitamins can influence the results. Blood thinners like warfarin, heparin, and aspirin may affect APTT outcomes. Other drugs, including antihistamines and chlorpromazine, as well as supplements like vitamin C, can also impact test results.

Preparations Before the Test

No special preparation is required prior to an APTT test. If you are taking any of the medications, supplements, or vitamins mentioned earlier, inform your doctor, as these substances may affect test results and lead to inaccuracies. You can continue your usual activities, and there are no restrictions on eating, drinking, or fasting before the test.

Test Procedure

The test utilizes blood samples obtained from the veins. First, the healthcare professional will identify the blood sampling site, typically the crease of the arm. Second, a tourniquet will be applied to the arm, and the individual will be instructed to clench their fist. Third, the skin at the sampling site will be disinfected with antiseptic fluid, such as an alcohol swab or cotton. Fourth, once the area is dry, the professional will insert the syringe needle at the designated site. Fifth, blood will be drawn into the syringe tube, with a volume of approximately 3mL to 5mL collected as needed. Sixth, the tourniquet will be removed, the syringe needle will be withdrawn from the injection site, and the site will be pressed with alcohol cotton. The blood sample is then ready for transport to the laboratory.

Normal and Abnormal Values

The APTT test is calculated using a time standard in seconds. In the test, the time required for the patient's blood sample to clot will be compared with the control sample at the same time.

Normal Values

The normal value of the APTT test is 25-35 seconds. This time indicates the normal time range for blood to clot.

Prolonged APTT

An abnormal value occurs if the time is longer than 35 seconds. This indicates a disorder in the blood clotting factor, causing the blood to take longer to clot. This condition can lead to bleeding that does not stop and significant blood loss from the body.

Shortened APTT

If the APTT test results are shorter, namely below 25 seconds, it is called a slow APTT. However, this condition is very rare. If the APTT test results are shortened, blood clotting occurs faster, increasing the risk of thrombosis (blood clots).

Results and Recommendations (Further Testing)

Prolonged APTT

If your APTT test results are abnormal, specifically above 35 seconds, it is referred to as a prolonged APTT. This indicates that it takes longer for your blood to clot than normal, suggesting a disorder or problem with the clotting factor in your body, a lack of clotting factor, or a disruption in the formation of clotting factors. This can occur in various blood clotting disorders, including hemophilia, vitamin K deficiency, von Willebrand disease, liver disease, leukemia, and the use of blood thinners such as warfarin and heparin. However, the APTT test cannot specifically determine the cause of blood clotting disorders, so additional tests are needed, such as ACT (Activated Whole Thrombin), PT (Prothrombin Time), TT (Thrombin Time), Von Willebrand factor, and platelet count. These additional tests can assist the doctor in accurately diagnosing blood clotting factor disorders. Additionally, the doctor will consider your symptoms, family history of blood clotting factor diseases, and the findings from their physical examination, as most blood clotting disorders are genetically inherited.

Shortened APTT

APTT test results can also indicate a shorter time, specifically under 25 seconds. However, this condition is very rare and can increase the risk of blood clotting in blood vessels, potentially leading to thrombosis or a higher occurrence of blood clots than normal.

Consult the Right Doctor

Consult your nearest internist if your APTT test results are abnormal or if your doctor in charge at the hospital is available. If your child experiences this, consult a pediatrician or the doctor in charge at the hospital, so that an evaluation of the test results can be performed and the doctor can carry out further examinations. This will help identify the cause of your abnormal APTT test results.

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