PT – Prothrombin Time:
Why PT – Prothrombin time Test?
CLINICAL INFORMATION
A blood clot is a gelatinous mass of fibrin and blood cells formed by the coagulation of blood. Blood clotting is an important process that prevents excessive bleeding. Blood platelets and plasma proteins (also referred to as coagulation or clotting factors) in the blood work together to stop bleeding by forming a clot over the injury. In the process of wound healing, the clot to dissolves naturally. But rarely, the blood clot without any injury, intravascular clots may be formed inside the blood vessels, that don’t dissolve, hence might lead to complications such as DVT, pulmonary embolism etc. Prothrombin (also known as factor-II) is a protein synthesized by the liver, which gets converted to thrombin, and helps in forming blood clots when exposed to injury. It is one among several substances (coagulation or clotting factor) present in the plasma protein that involves in the clotting mechanism (i.e in the blood coagulation cascade). High-risk factors for developing blood clots include smoking, trauma, oral contraceptives, certain types of cancers, family history of blood clots, high BP causing stroke, diabetes, obesity, pregnancy, immobilization (eg. due to hip bone fractures) etc.Clinical manifestations of a blood clot includes angina (heartburn), chest pain, discomfort in the upper region of the body, shortness of breath, sweating, nausea, lightheadedness, weakness in the face, arms, and legs, difficulty in speaking, headache, dizziness, vision problems, sudden or gradual swelling, tenderness, warmth in the extremities, increased heart rate, sweating, fever, coughing up blood, abdominal pain, vomiting, diarrhoea etc. Causes for slow blood clotting include blood-thinning medications, liver pathologies, absence or inadequate clotting factors in the blood, vitamin K deficiency, medications (such as Coumadin – commercial warfarin drug, heparin, aspirin, clopidogrel, thrombin inhibitors, factor Xa inhibitors, infusion of anticoagulants like protein-C & protein-S, steroids, antibiotics, antacids) that interfere with clotting mechanism etc. Blood thinners such as warfarin can be prescribed as medication for certain pathologies such as irregular heartbeat (atrial fibrillation), prosthetics (artificial heart valves), DVT, DIC, Pulmonary Embolism, anti-phospholipid syndrome, parents with a high risk of heart attacks (stroke) etc. Prothrombin time measures the time taken for the formation of the blood clot. The calculation of PT results is based on the prothrombin ratio (PR) and INR (International Normalized Ratio: INR ratio allows for easier comparison of test results from different laboratories). Hence this Prothrombin time test also known as protime INR and PT/INR, helps in the assay for evaluation of extrinsic pathways and common pathways of the coagulation cascade. Prothrombin time is monitored for screening in conditions such as patients with abnormal bleeding (bleeding disorders) and/or bruising, unexplained bleeding, unexplained nose bleeds, bleeding gums, blood in urine, blood in stools, unexplained heavy menstrual bleeding, DIC, unexplained blood clot in arteries and/or veins, the prognosis for medications such as warfarin (oral anticoagulant), blood-thinners to fix an accurate dose (since it has a narrow therapeutic window), pre-surgical requisite, excessive clotting disorder, evaluation – scoring system for assessing the severity of chronic liver diseases (eg. end-stage liver disease), haemophilia (bleeding disorder), abnormal platelet count, von-Willebrand disease, Lupus coagulant testing, to monitor infused intravenous anticoagulants like protein-C & protein-S, vitamin K deficiency, immune system disorders, diseases of the bone marrow etc. Prothrombin Time Test is also called as Pro-Time Test. This test procedure involves the addition of tissue factors to the patient’s blood plasma. Factors that could interfere with this test results include blood thinner medications such as warfarin (oral anticoagulant), OCPs etc. Hence prerequisite for this test is to stop such medications eg. warfarin and heparin (anticoagulants), thrombin inhibitors, factor Xa inhibitors, steroids, antibiotics, antacids, nutritional supplements, blood thinner – aspirin and clopidogrel, antacids, antihistamines, vitamin K, Heparin – eg. low molecular weight heparin etc), infusion of anticoagulants like protein-C & protein-S that would hamper the normal test results. Moreover, PT is often used in conjunction with the activated partial thromboplastin time (aPTT) which measures the intrinsic pathway and common pathway of coagulation. Additional tests include partial thromboplastin time (PTT) test, thrombin time, thrombocytes – for platelet function, estimation of vitamin K, screening for clotting factors in the extrinsic (i.e PT evaluates coagulation factors in the extrinsic and common pathway eg. coagulation factor-I or fibrinogen, factor-II or prothrombin, factor- V or proaccelerin, factor-VII or proconvertin, factor- X or Stuart-Prower factor etc), intrinsic (i.e PT/INR evaluates coagulation factors in intrinsic and common pathway eg. coagulation factor-XII, factor-XI, factor-IX, factor-VIII, factor-X, factor-V, factor-II, factor-I, as well as prekallikrein-PK and high molecular weight kininogen-HK). Other tests include CBC, peripheral blood smear examination, differential count, ESR, bleeding time etc.
General Instructions:
Sample Requirement: Specimen - Blood sample collected from the vein. Test Preparation: None.
NOTE - Sample for specimen collections may vary based on the patient’s condition/cases according to the patient’s presenting complaints/signs or symptoms:
SPECIMEN REQUIREMENT (Special or Rare Cases) - As instructed and guided by Physician / Clinician / Pathologist / as per Laboratory’s requirements, according to procedures and protocols.
This Multi-Specialty Clinical Referral Laboratory RT DIAGNOSTICS provides precise and accurate tests with an extensive range of testing services to the medical centres to help in the diagnosis and identification of pathology in the test specimens for infectious diseases and also to evaluate the function of organ systems of the patient. It prevents further complications and helps to stabilize and restore health to near normalcy at the earliest without delay.
