Dr. Saoji Orthopaedic Clinic And Medilab Pathology Laboratory
Sky Orthopaedics,1st Floor, Nikalas Tower, Central Bazar Road,Nagpur
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Know About Prothrombin Time (PT) (Citrated plasma)
The prothrombin time (PT) is a test that helps evaluate a person's ability to appropriately form blood clots. The international normalized ratio or INR is a calculation based on results of a PT that is used to monitor individuals who are being treated with the blood-thinning medication (anticoagulant) warfarin (Coumadin?).
A PT measures the number of seconds it takes for a clot to form in a person's sample of blood after substances (reagents) are added. The PT is often performed with a partial thromboplastin time (PTT) and together they assess the amount and function of proteins called coagulation factors that are an important part of proper blood clot formation.
In the body, when there is an injury and bleeding occurs, the clotting process called hemostasis begins. This process involves in part a series of sequential chemical reactions called the coagulation cascade, in which coagulation or "clotting" factors are activated one after another and result in the formation of a clot. There must be a sufficient quantity of each coagulation factor, and each must function properly, in order for normal clotting to occur. Too little can lead to excessive bleeding; too much may lead to excessive clotting.
In a test tube during a laboratory test, there are two "pathways" that can initiate clotting, the so-called extrinsic and intrinsic pathways. Both of these then merge into a common pathway to complete the clotting process. The PT test evaluates how well all of the coagulation factors in the extrinsic and common pathways of the coagulation cascade work together. Included are: factors I (Fibrinogen), II (Prothrombin), V, VII and X. The PTT test evaluates those protein factors that are part of the intrinsic and common pathways: XII, XI, IX, VIII, X, V, II (prothrombin), and I (fibrinogen) as well as prekallikrein (PK) and high molecular weight kininogen (HK). The PT and PTT evaluate the overall ability to produce a clot in a reasonable amount of time and, if any of these factors are deficient in quantity or not functioning properly, the test results will be prolonged.
The PT test is usually measured in seconds and is compared to a normal range that reflects PT values in healthy individuals. Because the reagents used to perform the PT test vary from one laboratory to another and even within the same laboratory over time, the normal ranges also will fluctuate. To standardize results across different laboratories in the U.S. and the world, a World Health Organization (WHO) committee developed and recommended the use of the Internationalized Normalized Ratio (INR), calculated based on the PT test result, for people who are receiving the anticoagulant warfarin (Coumadin?).
The INR is a calculation that adjusts for changes in the PT reagents and allows for results from different laboratories to be compared. Most laboratories report both PT and INR values whenever a PT test is performed. The INR should be only applicable, however, for those taking the blood-thinning medication warfarin.
PT; Pro Time; Protime; INR; Prothrombin Time and International Normalized Ratio.
Prevent Blood Clots;
A prothrombin time (PT) is a test used to help detect and diagnose a bleeding disorder or excessive clotting disorder; the international normalized ratio (INR) is calculated from a PT result and is used to monitor how well the blood-thinning medication (anticoagulant) warfarin (Coumadin?) is working to prevent blood clots..When you are taking warfarin or when you have unexplained or prolonged bleeding or inappropriate blood clotting.
A PT and INR are ordered on a regular basis when a person is taking the anticoagulant drug warfarin to ensure that the prescription is working properly and that the PT/INR is appropriately prolonged. There is no set frequency for doing the test. A health practitioner will order them often enough to make sure that the drug is producing the desired effect - that it is increasing the person's clotting time to a therapeutic level without significant risk of excessive bleeding or bruising.
The PT may be ordered when a person who is not taking anticoagulant drugs has signs or symptoms of excessive bleeding or clotting, such as:
Unexplained bleeding or easy bruising
A blood clot in a vein or artery
An acute condition such as disseminated intravascular coagulation (DIC) that may cause both bleeding and clotting as coagulation factors are used up at a rapid rate
A chronic condition such as severe liver disease that may affect hemostasis
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, such as frequent or excessive nosebleeds and easy bruising, which may indicate the presence of a bleeding disorder.