Partial Thromboplastin Time

Partial Thromboplastin Time 

The PTT should be 25 to 35 seconds. If the person is taking blood thinners, clotting takes longer

Partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are used to test for the same functions; however, in aPTT, an activator is added that speeds up the clotting time and results in a narrower reference range. The aPTT is considered a more sensitive version of the PTT and is used to monitor the patient’s response to heparin therapy.

The reference range of the aPTT is 30-40 seconds. The reference range of the aPTT is 30-40 seconds. [1, 2, 3]

The reference range of the PTT is 60-70 seconds.

In patients receiving anticoagulant therapy, the reference range is 1.5-2.5 times the control value in seconds.

Critical values that should prompt a clinical alert are as follows:

aPTT: More than 70 seconds (signifies spontaneous bleeding)

PTT: More than 100 seconds (signifies spontaneous bleeding 

Interpretation

A prolonged aPTT result may indicate the following [1, 2] :

Congenital deficiencies of intrinsic system clotting factors such as factors VIII, IX, XI, and XII, including haemophilia A and haemophilia B (Christmas disease), two inherited bleeding disorders resulting from a deficiency in factors VIII and IX, respectively

Congenital deficiency of Fitzgerald factor (prekallikrein)

Von Willebrand disease, which is the most common inherited bleeding disorder, affecting platelet function owing to decreased von Willebrand factor activity

Hypofibrinogenemia

Liver cirrhosis (the liver makes most of the clotting factors, including those that are vitamin K-dependent ones); diseases of the liver may result in an inadequate quantity of clotting factors, prolonging the aPTT

Vitamin K deficiency: The synthesis of some clotting factors requires vitamin K, so vitamin K deficiency results in an inadequate quantity of intrinsic system and common pathways clotting factors, as a result, the aPTT is prolonged

Disseminated intravascular coagulation (DIC): The clotting factors involved in the intrinsic pathway are consumed, prolonging the aPTT

Heparin therapy, which inhibits the intrinsic pathway at several points (eg, prothrombin II), prolongs the aPTT [4]

Coumarin therapy, which inhibits the function of factors I, IX and X, prolongs the aPTT

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

Specific circulating anticoagulants, inhibitor antibodies that specifically target certain coagulation factors, such as in individuals with haemophilia after many plasma transfusions, systemic lupus erythematosus, rheumatoid arthritis, tuberculosis, and chronic glomerulonephritis

A shortened aPTT result may indicate the following [1, 2] :

Early stages of DIC: circulating procoagulants exist in the early stages of DIC, shortening the aPTT

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

Immediately after acute haemorrhage

An acute-phase response leading to high factor VIII levels

Inputs Courtesy: ENT Specialist Doctor with 41 years of experience. He can be reached only by WhatsApp messages at 9243301223.