What is prothrombin time checked for

Prothrombin time is mainly used to evaluate the function of exogenous coagulation pathways, including the activity of coagulation factors II, V, VII, X and fibrinogen levels. It is commonly used to monitor anticoagulant therapy, diagnose bleeding disorders or liver dysfunction.

1. Coagulation factor detection:

Prothrombin time directly reflects the activity levels of coagulation factors II, V, VII, and X in plasma. These factors are synthesized by the liver and participate in the activation process of exogenous coagulation pathways. When the factor activity is below 50% of the normal value, the prothrombin time will be significantly prolonged.

2. Anticoagulant therapy monitoring:

Patients taking vitamin K antagonists such as warfarin should have their prothrombin time regularly tested. The drug exerts anticoagulant effects by inhibiting the synthesis of vitamin K-dependent coagulation factors II, VII, IX, and X. The test results are reported in the form of international standardized ratios, and the treatment target value is usually 2.0-3.0.

3. Liver function assessment:

The liver is the main site for the synthesis of coagulation factors, and patients with liver diseases such as cirrhosis and hepatitis often have prolonged prothrombin time. When liver cell damage exceeds 70%, the synthesis of coagulation factors is significantly reduced, which can be used as a sensitive parameter to judge the severity of liver disease.

4. Hemorrhagic disease screening:

Hereditary coagulation factor deficiency, such as hemophilia B factor IX deficiency, can be diagnosed with prothrombin time assistance. This examination can distinguish between endogenous and exogenous coagulation pathway abnormalities, and combined with activated partial thromboplastin time detection, can locate specific defective links.

5. Diagnosis of disseminated intravascular coagulation:

During disseminated intravascular coagulation, a large amount of coagulation factors are consumed, and both prothrombin time and activated partial thromboplastin time are prolonged. Dynamic monitoring of this indicator helps to determine the progression of the disease, and when the value exceeds 1.5 times the normal value, it indicates severe coagulation dysfunction.

Before testing, one should maintain a normal diet and avoid vigorous exercise that may affect the accuracy of the results. Insufficient or excessive intake of vitamin K may interfere with the detection value. It is recommended to maintain a stable dietary structure for the first 3 days of the examination. Long term use of antibiotics and antiepileptic drugs should be informed in advance that some drugs may cause false abnormal results by affecting vitamin K metabolism. After blood collection, press the puncture point for more than 5 minutes. For those with abnormal coagulation function, the compression time should be extended to 15 minutes. It is recommended to have a fixed testing institution for regular monitoring of the population, as differences in laboratory reagents may lead to fluctuations in values.