Difference Between PTT and aPTT (With Table)

Partial Thromboplastin Time (PTT) and activated Partial Thromboplastin Time (aPTT) are two types of medical tests that evaluate and characterize blood coagulation. With the help of these tests, medical experts can evaluate bleeding and coagulation disorders and the intrinsic pathways of various coagulation factors. In the aPTT test, an activator is added while in the PTT test there is no activator. 

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PTT vs aPTT

The main difference between PTT and aPTT is that in the PTT test there is no activator hence there is no chance to elevate the speed of the clotting time. In the case of aPTT, an activator is added which elevates the speed of clotting time and results can be obtained at a narrower reference range. This is why the reference range of PTT is 60-70 seconds whereas the reference range of aPTT is 30-40 seconds. 

In simple words, PTT is a medical test that is conducted to evaluate the total time it takes in a person for the blood to clot. These help to diagnose several bleeding disorders such as hemorrhage and thrombosis. For the PTT test, oxalate or citrate is added to a test tube in which the blood sample is collected. 

aPTT is also a medical test for blood coagulation but instead of measuring the time taken for blood clotting, it evaluates the clotting factors of the intrinsic pathway. An activator is used in this test to make the clotting time faster and it is also more sensitive to heparin therapy. 

Comparison Table Between PTT and aPTT

Parameters of Comparison

PTT

aPTT

Definition

PTT is a type of test that measures the time taken for blood clotting to diagnose coagulation disorders. 

aPTT is the test of activated blood coagulation that measures the effectiveness of heparin. 

Significance

PTT mainly evaluates both the quantity and the performance of several proteins that are known as coagulation factors. 

aPTT investigates clotting factors I (fibrinogen), II (prothrombin), V, VIII, IX, X, XI, and XII. 

Functions

PTT primarily acts as a probe for unexplained bleeding or clotting in any body parts. The test helps in assessing hemostasis. 

aPTT is used as a medical screening test to evaluate the intrinsic pathways of the clotting factors. 

Clotting Factors

PTT evaluates and measures the clotting factors VIII, IX, X, and XII. 

aPTT evaluates and measures the clotting factors V, VIII, IX, X, XI, and XII. 

Heparin Sensitivity

PTT is less sensitive to heparin which is an anticoagulant. 

aPTT is more sensitive to heparin as compared to PTT. 

Reference Range

60-70 seconds is the reference range of PTT and it is the regular time of blood clotting. 

30-40 seconds is the reference range of aPTT and it is narrowed by adding an activator.  

Critical Values

If the PTT value exceeds 100 seconds it implies spontaneous bleeding.

If aPTT value exceeds 70 seconds it implies spontaneous bleeding. 

What is PTT?

PTT is a medical test to measure the time for blood to clot. A PTT test checks the functions of specific coagulation factors if any of these are missing or showing abnormal behavior. The most common bleeding disorder is hemophilia. So, PTT helps in finding out if there is excessive bleeding or excessive blood clot. 

There are several reasons why one should take a PTT test. If a person suffers from heavy bleeding or bruised easily should take a PTT test. Many people have a blood clot in a vein or artery which increases the risk of heart attacks and strokes. 

PTT tests can analyze multiple body disorders only by evaluating the clotting time. For example, it can diagnose any liver disease, vitamin K deficiency, and autoimmune diseases like lupus anticoagulant syndrome. 

What is aPTT?

aPTT is also a blood coagulation test that investigates the coagulation factors of the intrinsic pathways. In this test, an activator is used so that the blood clotting time is narrowed down to 30-40 seconds. An aPTT test can find out how different clotting factors are working in a person’s body. 

This test is very useful to monitor blood coagulation in those who are undergoing heparin therapy. Large doses of warfarin might affect the results of this test. So, it is also wise to consult a medical expert before undergoing this test. 

aPTT test is a much-advanced test for blood coagulation performance and thus it has replaced many PTT tests. Decalcified blood is used for this test and it can diagnose the deficiency of coagulation factors V, VII, IX, X, XI, and XII in the blood. 

Main Differences Between PTT and aPTT

  1. PTT is a type of test that measures the time taken for blood clotting to diagnose coagulation disorders.  On the other hand, aPTT is the test of activated blood coagulation that measures the effectiveness of heparin. 
  2. PTT mainly evaluates both the quantity and the performance of several proteins that are known as coagulation factors. But, aPTT investigates clotting factors I (fibrinogen), II (prothrombin), V, VIII, IX, X, XI, and XII. 
  3. PTT primarily acts as a probe for unexplained bleeding or clotting in any body parts whereas aPTT is used as a medical screening test to evaluate the intrinsic pathways of the clotting factors. 
  4. PTT evaluates and measures the clotting factors VIII, IX, X, and XII whereas aPTT evaluates clotting factors V, VIII, IX, X, XI, and XII. 
  5. PTT is less sensitive to heparin which is an anticoagulant whereas aPTT is more sensitive to heparin as compared to PTT. 
  6. 60-70 seconds is the reference range of PTT and it is the regular time of blood clotting. But, 30-40 seconds is the reference range of aPTT and it is narrowed by adding an activator.  
  7. The critical value of PTT is 100 seconds whereas for aPTT it is 70 seconds. 

Conclusion

Though PTT and aPTT have various features, they are both types of medical tests that are used to investigate and evaluate blood coagulation disorder. In both tests, blood plasma is used. 

These tests are important because it is necessary to evaluate any blood coagulation disorder. The very little capability of clotting can increase the risk of excessive bleeding whereas excessive blood clotting can obstruct the blood flow. 

References

  1. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0609.1980.tb01341.x
  2. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1751-553X.2010.01261.x

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