What is prothrombin time checked for

Prothrombin time is mainly used to evaluate the function of exogenous coagulation pathways and is an important indicator for diagnosing hemorrhagic diseases and monitoring anticoagulant therapy. Abnormal prothrombin time may be caused by factors such as vitamin K deficiency, liver disease, warfarin use, genetic coagulation factor deficiency, disseminated intravascular coagulation, etc.

1. Coagulation function assessment:

Prothrombin time reflects the status of exogenous coagulation pathways by detecting the activity of coagulation factors I, II, V, VII, and X in plasma. This examination requires the collection of venous blood, the addition of tissue factors and calcium ions, and the measurement of plasma coagulation time. The normal value is usually 11-14 seconds, and if it exceeds the normal range for more than 3 seconds, it indicates an abnormality.

2. Anticoagulant therapy monitoring:

Patients taking vitamin K antagonists such as warfarin should have their prothrombin time regularly tested. The international standardized ratio can eliminate differences in reagents, and the treatment range is generally 2.0-3.0. A low value may increase the risk of thrombosis, while a high value may lead to bleeding complications.

3. Liver disease screening:

The liver is the main organ for synthesizing clotting factors, and patients with liver diseases such as cirrhosis and hepatitis often have prolonged prothrombin time. When liver synthesis function decreases by 70%, prothrombin time is significantly abnormal and can be used as an auxiliary indicator to evaluate the severity of liver disease.

4. Diagnosis of bleeding etiology:

Genetic coagulation factor deficiencies such as hemophilia B and acquired vitamin K deficiency can lead to prolonged prothrombin time. When neonatal hemorrhagic diseases and biliary obstruction affect the absorption of fat soluble vitamins, abnormal indicators often appear earlier than clinical symptoms.

5. Early identification of DIC:

In the early stage of disseminated intravascular coagulation, prolonged prothrombin time may occur due to the consumption of coagulation factors, accompanied by decreased platelets and fibrinogen. Dynamic monitoring can help identify coagulation dysfunction secondary to serious infections, malignant tumors, and other diseases. Before the prothrombin time test, vigorous exercise and a high-fat diet should be avoided. Long term use of antibiotics or antiepileptic drugs may affect the accuracy of the results. When abnormal indicators are found, further examination should be conducted in combination with activated partial thromboplastin time, platelet count, etc. Daily diet can appropriately increase green leafy vegetables rich in vitamin K, but those taking warfarin need to maintain stable intake of vitamin K. Regular follow-up is of great significance for evaluating treatment efficacy and adjusting medication plans.