Diagnostic Index Of Blood Coagulation Function

Author: Succeeder    

Blood coagulation diagnostic are routinely prescribed by doctors. Patients with certain medical conditions or those who are taking anticoagulant drugs need to monitor blood coagulation. But what do so many numbers mean? Which indicators should be monitored clinically for different diseases?

Coagulation function test indexes include prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (FIB), Clotting time (CT) and International normalized ratio (INR), etc., several items can be selected to make a package, which is called coagulation X item. Due to the different detection methods used by different hospitals, the reference ranges are also different.

PT-prothrombin time

PT refers to adding tissue factor (TF or tissue thromboplastin) and Ca2+ to the plasma to start the extrinsic coagulation system and observe the coagulation time of the plasma. PT is one of the most commonly used screening tests in clinical practice to evaluate the function of extrinsic coagulation pathway. The normal reference value is 10 to 14 seconds.

APTT - activated partial thromboplastin time

APTT is to add XII factor activator, Ca2+, phospholipid to the plasma to initiate the plasma endogenous coagulation pathway, and observe the plasma coagulation time. APTT is also one of the most commonly used screening tests in clinical practice to evaluate the function of the intrinsic coagulation pathway. The normal reference value is 32 to 43 seconds.

INR - International Normalized Ratio

INR is the ISI power of the ratio of the PT of the tested patient to the PT of the normal control (ISI is an international sensitivity index, and the reagent is calibrated by the manufacturer when it leaves the factory). The same plasma was tested with different ISI reagents in different laboratories, and the PT value results were very different, but the measured INR values ​​were the same, which made the results comparable. The normal reference value is 0.9 to 1.1.

TT-thrombin time

TT is the addition of standard thrombin to the plasma to detect the third stage of the coagulation process, reflecting the level of fibrinogen in the plasma and the amount of heparin-like substances in the plasma. The normal reference value is 16 to 18 seconds.


FIB is to add a certain amount of thrombin to the tested plasma to convert the fibrinogen in the plasma into fibrin, and calculate the content of fibrinogen through the turbidimetric principle. The normal reference value is 2 to 4 g/L.

FDP-plasma fibrin degradation product

FDP is a general term for degradation products produced after fibrin or fibrinogen is decomposed under the action of plasmin produced during hyperfibrinolysis. The normal reference value is 1 to 5 mg/L.

CT-coagulation time

CT refers to the time when blood leaves blood vessels and coagulates in vitro. It mainly determines whether various coagulation factors in the intrinsic coagulation pathway are lacking, whether their function is normal, or whether there is an increase in anticoagulant substances.