Prothrombin time (PT) Lab Test

Prothrombin time (PT)
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Clinical Definition of Prothrombin time (PT)

A prothrombin time (PT) test measures the time it takes for a clot to form in a blood sample. A clot is a thick lump of blood that the body produces to seal leaks, wounds, cuts and scratches and prevent excessive bleeding. 12 blood clotting factors are needed for blood to clot (coagulation). Prothrombin or factor II is one of the clotting factors made by the liver. Vitamin K is needed to make prothrombin and other clotting factors. The PT test evaluates, the integrated function and the action of five different clotting (coagulation) factors (I, II, V, VII, and X). It evaluates the body’s ability to produce a clot within a reasonable amount of time. If any factor is missing, deficient, or defective, clotting time is delayed, the PT is prolonged. It is also used to check for bleeding problems.

How do You Understand the Result?

The test is designed to tell us how quickly the blood clots. There is no normal value, and it varies depending on the lab used for the test. Post receiving the results, it is best to consult the doctor to understand what the result signifies.

Again depending from lab to lab, the results might be received in a matter of hours, or in a few days.

The normal Prothrombin Time (PT) test value is 10-14 seconds. Anything higher would be an indication that the blood is taking more time than the usual to clot, this being an area of concern. Additionally, it might also signify that the person is suffering from one of the following conditions –

• Liver disease

• Lack of clotting factors

• Lack of vitamin K

• Clotting or Bleeding disorder

Further, there are instances where the value is lower, indicating the blood is clotting faster. This could be due to eating foods rich in Vitamin K or the intake of supplements.

Why do I need Prothrombin Time Test?

The Prothrombin time (PT) test is a test used to check if the person is suffering from a bleeding disorder. The symptoms are as follows –

• Easy bruising

• Nosebleeds that won't stop

• Excessive bleeding after dental appointments

• Heavy menstrual periods

• Blood in the urine

• Swollen or painful joints

Further, there are certain drugs, which tend to thin the blood, like warfarin (Coumadin, Jantoven). The PT test helps guide the doctors to understand the dosage which will prevent excessive clotting; however, still clot the blood when required.

Additionally, the doctor might ask for the PT test, in case the individual is suffering from one of the following ailments –

• Normal blood clotting before having a surgery

• Liver concerns

• Lack of vitamin K

• Immune system concerns

• Certain cancers, like leukaemia

• Bone marrow concerns

What other tests might I have along with Prothrombin Time Test?

Depending on the symptoms and what the doctor suspects, they might ask for additional tests to be conducted. In case the doctor suspects that there is a problem with the liver, he/she might suggest a test to ensure that the liver is functioning correctly.

Similarly, if the doctor suspects a bleeding disorder, he/she might request for one of the following tests to be conducted additionally along with the Prothrombin time (PT) Test –

• von Willebrand factor test (shows the presence of any genetic disorders that could cause bleeding problems or nosebleeds)

• Thrombin time test

Platelet count

PTT test

When do you expect results?

The PT test results can be expected right away. There is no wait time required for the test results. It a test quickly done in a few minutes; however, it also depends on the lab where the test is being conducted.

What is a Prothrombin time (PT)?

When we hurt ourselves, like with all ailments, the body starts working on the wound. The platelets in our body, which are a type of cell in the body, reach the wound area to reduce the bleeding. Post that the proteins, called the clotting factors, bunch up together and form a blood clot. Thus the wound stops bleeding and then the healing process begins. This is what the ideal situation would be when you hurt yourself.

However, in certain individuals, the clotting happens when it shouldn’t and when they hurt themselves, the bleeding doesn’t stop easily. This is alarming and an indication of a problem. Here is when the doctor recommends a Prothrombin Time Test, to understand how quickly the blood clots.

How is Prothrombin Time Test done?

The Prothrombin Time (PT) test is like any other simple blood test. The doctor would draw blood from mostly the vein in your arm or, in rare cases, from the back of your hand. The entire procedure barely takes a few minutes. The steps that the healthcare provider would follow the simple routine of first cleaning the skin over the vein. Then they would tie an elastic band around the arm, to have the vein filled with blood faster. Post that, depending on easy it’s for the doctor to locate the vein, the needle would be inserted into the vein, and the blood would be drawn. The blood is stored on a sterile vial connected to the needle. The puncture site is covered with gauze or adhesive bandage to stop the blood from flowing. The blood collected in the sterile vial is then used for further tests.

Does Prothrombin Time Test pose any risk?

Since the blood test is fairly simple, the chances of any risk or complication are very rare. Since there is a needle being used the puncture the vein and obtain the blood, in rare case scenarios, one of the following might occur –

• pain

• bleeding

• bruising

• infection

In case you start feeling nauseous or light-headed when the blood is being drawn, please inform the same to the doctor right way.

How do I prepare for Prothrombin Time Test?

Since this is a very simple test, there is no preparation required for the same. The only thing to remember not everyone is comfortable with blood being taken. In case of any questions, please ask the doctor before the test. And if you feel nauseous or faint, please inform the practitioner.

In short,

No Fasting Required.

No other special preparations required.

Sample Required?

Specimen type: Serum (Blood Sample)

Specimen collection procedure: Venipuncture (Collection of blood from a vein, usually from the arm)

Prothrombin time (PT) Test Price

The Prothrombin time (PT) Test is priced in the range of Rs 200 to Rs. 500.

Understanding results of Prothrombin time (PT)

Reference RangeInterpretation
10 to 15 SecondsGender :Female
0.99Gender : Prothrombin ratio
10 – 15 secondsGender :Male
Below 17secondsGender :New born
2 to 3Gender :International normalized Ratio (I.N.R)

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’