Prothrombin is a protein produced by the liver that plays a role in blood coagulation (clotting). The human body has at least 12 coagulation factors, including prothrombin and fibrinogen. A Prothrombin Time Test (PTT) is a blood test that determines how long it takes for blood to clot. Normally, human blood is in liquid form but must have the ability to clot to prevent excessive bleeding. However, blood that clots too quickly can also pose health risks.
Typically, a Prothrombin Time Test is conducted alongside another clotting test, Partial Thromboplastin Time (PTT), to assess how well other coagulation factors function. The Prothrombin Time Test is also known as the International Normalized Ratio (INR) test.
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Purpose of the Prothrombin Time Test
The main goal of a Prothrombin Time Test is to evaluate how well blood can clot. The results help doctors diagnose conditions or assess ongoing treatment effectiveness.
The Prothrombin Time Test is performed to:
- Monitor the effectiveness of blood-thinning medications (such as Warfarin) in preventing blood clots.
- Identify the cause of excessive blood clotting.
- Diagnose unusual bleeding disorders.
- Assess blood clotting ability before surgery to prevent excessive bleeding.
- Diagnose liver disorders, including liver disease or pre-transplant evaluations.
- Detect vitamin K deficiency.
When is a Prothrombin Time Test Needed?
Your doctor may recommend a Prothrombin Time Test if you experience the following conditions:
- Regular consumption of Warfarin.
- Unexplained heavy bleeding.
- Easy bruising.
- Frequent nosebleeds.
- Heavy menstrual bleeding.
- Pre-surgery screening.
Procedure
A Prothrombin Time Test requires a blood sample. Usually, fasting is not necessary before the test. However, certain medications and vitamin K supplements should be avoided to prevent skewed results.
A lab technician will collect a blood sample from a vein in the upper arm or the back of the hand. The sample is then analyzed in a laboratory.
Understanding Prothrombin Time Test Results
Prothrombin Time Test results are typically presented in two formats: INR (International Normalized Ratio) or seconds. INR is more commonly used, particularly to monitor Warfarin effectiveness.
Normal Prothrombin Time Test Results:
- INR: 0.8 – 1.1 (if not taking Warfarin)
- INR: 2.0 – 3.0 (if taking Warfarin)
- PT: 11 – 13.5 seconds
What Do Abnormal Results Indicate?
A Prothrombin Time Test result is considered abnormal if it falls outside the normal range.
High PT/INR: Blood takes longer than usual to clot. This may indicate:
- Blood-thinning medication use (requiring dosage adjustment by a doctor).
- Deficiency in coagulation factors.
- Liver disorders.
- Vitamin K deficiency.
- Blood disorders like hemophilia.
Low PT/INR: Blood clots too quickly, increasing the risk of blockages in blood vessels. Causes include:
- Vitamin K supplement consumption.
- Diet rich in vitamin K.
- Hormone therapy medications, especially those containing estrogen.
- Excessive Warfarin dosage (requires adjustment by a doctor).
- Excessive alcohol consumption.
Side Effects
This test is generally safe, with minimal side effects. Some individuals may experience mild bruising at the blood collection site, which usually disappears within a few days. Rarely, minor bleeding may occur.
If you experience any of the following symptoms, seek medical consultation immediately:
- Frequent bruising or nosebleeds.
- Bleeding that is difficult to stop.
- Chest pain.
- Leg swelling.
- Red or darkened skin on the legs.
If you need a Prothrombin Time Test, consult with a hematology specialist or internal medicine doctor. You can visit the Advanced Cancer and Radiotherapy Centre at Mandaya Royal Hospital Group for expert medical consultations.
Book an appointment via WhatsApp Chat, Online Booking, or download the Care Dokter app on Google Play and the App Store today!
