Activated partial thromboplastin time

Activated partial thromboplastin time (APTT) is a special medical test that simulates the process of blood clotting along the internal pathway, aimed at assessing the presence of plasma factors, inhibitors and anticoagulants in the blood.

It shows the effectiveness of the internal mechanism of blood clotting, allows you to diagnose hemophilia and monitor patients undergoing heparin and gerudin therapy.


For an adult, the APTT rate is considered from 21 to 35 s. Lengthening aPTTV means that blood clots more slowly than necessary. This happens in cases when there are not enough clotting factors in the blood, or there are substances in the plasma that slow down the coagulation of blood.

It should be remembered that different equipment in the laboratory has its own specific norms. When the result is given to you, this indicator will be indicated in the column “reference values”.

APTTV - what is it?

ACHT is a period of time over which a blood clot appears, this occurs after calcium chloride or other reagents are added to the plasma. At present, the analysis is the most accurate indicator of the presence of diseases associated with blood coagulation.

The main indications for the appointment of AChWT:

  1. Diagnosis of hemophilia;
  2. General assessment of the blood coagulation system (identification of causes of thrombosis and bleeding;
  3. DIC (disseminated intravascular coagulation syndrome);
  4. Monitoring of anticoagulant therapy (treatment with heparin);
  5. Detection of coagulation factor deficiency along the internal path: II, V, VIII, IX, X, XI, XII.

Normally, a fibrin clot is formed within 21-35 seconds. The research method consists in the following manipulations:

  1. Produced intake of venous blood into a tube containing sodium citrate, which has the ability to bind calcium ions, responsible for blood clotting.
  2. After that, reagents are added to the tube that activate the internal coagulation pathway. Coalin or kefalin are most often used as reagents.
  3. The next step in the study is to add calcium chloride to the tube, to neutralize the anticoagulant effect of sodium citrate and restore hemostasis, and to estimate the rate of clot formation.

Before the study, you should follow recommendations such as a temporary refusal to take anticoagulant drugs, hunger for 12 hours prior to analysis and, if possible, quitting smoking for a day.

Causes of high or low APTT

If the APTT is higher than normal, this indicates that the patient has possible liver diseases or a lack of vitamin K in the body, and this may also indicate the presence of a lupus anticoagulant in the blood.

If the figures are below normal, this may be due to a decrease in blood clotting, the presence of hemophilia and the antiphospholipid syndrome. In addition, this deviation from the norm may be associated with intravascular coagulation syndrome. A low APTT is a symptom of intravascular coagulation, if there is a deviation, then the patient has a grade I disease.

APTT above normal - what does this mean?

Causes of lengthening above the normal activated partial thromboplastin time (APTT):

  1. Hemophilia A and B;
  2. Von Willebrand disease;
  3. Congenital deficiency of precalacrein and kinin;
  4. Administration of heparin or streptokinase;
  5. Condition after a large volume of blood transfusion;
  6. The presence of lupus anticoagulant in the blood;
  7. Antiphospholipid syndrome;
  8. Chronic glomerulonephritis;
  9. Systemic lupus erythematosus;
  10. Reception of anticoagulants (Warfarin, Sinkumarin, etc.);
  11. Vitamin K deficiency;
  12. Low fibrinogen in the blood;
  13. Liver disease;
  14. Phase II and Phase DIC;
  15. Deficiency of coagulation factors (II, V, VII, VIII, IX, X, XI, XII);
  16. Connective tissue diseases

As a rule, the high results of the APTT analysis indicate an increased risk of bleeding as a result of congenital or acquired deficiency of one or more coagulation factors.

APTT below normal - what does this mean?

Shortening of aPTT below normal indicates the prevalence of hypercoagulation and may be caused by the following reasons:

  1. Activation of the internal coagulation mechanism in thrombosis, thromboembolism. This may be due to the resistance of factor V to activated protein C, an increased level of factor VIII or activated clotting factors.
  2. In DIC syndrome (hypercaogulation phase).
  3. Perhaps with a normal pregnancy.

A decrease in APTT indicates a tendency to thromboembolism.

What influences the analysis results

How is decryption done? What specifically affects the result of this analysis?

  1. A blood test contaminated with heparin.
  2. A sufficiently high hematocrit is able to lengthen the APTT.
  3. The amount of blood taken for this analysis. The required ratio of blood taken and anticoagulant in the existing tube is 9: 1.
  4. Blood coagulation, when it leads to the consumption of various clotting factors, and also significantly changes the tolerance of the APTT.
  5. Such factors as fatty foods, smoking, menstruation cycle and the presence of pregnancy in women also have a lot of influence. These factors can lead to falsely reduced APTT values.

The APTT is very important to establish an accurate picture of the patient’s condition, especially during pregnancy. The results of the analysis allow not only to evaluate the work of the coagulation system, but also to reveal the presence of certain diseases. And the sooner the deviation from the norm of the APTT is detected, the easier and faster you can cope with the disease.

Watch the video: Surprises in Coagulation TestingProlonged APTT & PT Case Hot Topic (January 2020).


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