About the Test
Clotting is what prevents excessive bleeding when you cut yourself. But the blood moving through your vessels shouldn’t clot. If such clots form, they can travel through your bloodstream to your heart, lungs, or brain. This can cause a heart attack, stroke, or even death.
Coagulation tests measure your blood’s ability to clot, and how long it takes to clot. Testing can help your doctor assess your risk of excessive bleeding or developing clots (thrombosis) somewhere in your blood vessels.
There are many types of coagulation tests. Clinicians frequently order coagulation tests, such as the prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), Fibrinogen and D-dimer.
Prothrombin Time and International Normalized Ratio (PT/INR). A prothrombin time (PT) is a test used to help detect and diagnose a bleeding disorder or excessive clotting disorder. Results are given in the number of seconds it takes the blood to clot. The international normalized ratio or INR is a calculation based on results of a PT that is used to compare results of different laboratories and It’s also useful in monitoring those who take medications that affect clotting, such as warfarin (Coumadin).
Your doctor will usually order the PT test along with another clotting test called an activated partial thromboplastin time (aPTT). This test is a part of an investigation of a possible bleeding disorder or blood clot (thrombotic episode); it helps investigate recurrent miscarriages or diagnose antiphospholipid syndrome (APS); aPTT used to monitor unfractionated (standard) heparin anticoagulant therapy. PT, along with PTT, may be ordered prior to surgery when the surgery carries an increased risk of blood loss and/or when the person has a clinical history of bleeding.
Fibrinogen is a protein made by your liver. This test measures how much fibrinogen is in your blood. Abnormal results may be a sign of excessive bleeding or hemorrhage, fibrinolysis, or placental abruption, which is a separation of the placenta from the uterine wall.
Thrombin time measures how well fibrinogen is working. Abnormal results may be due to inherited fibrinogen disorders, liver disease, some cancers, and medications that affect clotting.
D-dimer is one of the protein fragments produced when a blood clot gets dissolved in the body. It is normally undetectable or detectable at a very low level unless the body is forming and breaking down blood clots. Then, its level in the blood can significantly rise.
Purpose of a coagulation test
Clotting disorders can cause a dangerous amount of bleeding or clotting. If your doctor suspects you have a clotting disorder, they may recommend one or more coagulation tests. These tests measure various proteins and how they function.
Conditions that can cause coagulation problems include:
thrombophilia, which is excessive clotting
hemophilia, which is an inability to clot normally
Coagulation tests are useful in monitoring people who take medications that affect clotting ability. Coagulation tests are also sometimes recommended before surgery.