1) Explain what the PT/INR lab test measures.
PT/INR refers to Prothrombin time (PT) and INR refers to International normalized ratio (INR). PT/INR test measures the clotting time of blood in seconds. PT test can be performed using various reagents and so INR method is used to standardize the results obtained through PT test regardless of the reagent used. PT/INR test is often used in anticoagulation therapy to monitor the patient’s response to the drug being administered (Poller, 2004).
2) List the type/color top tube used to collect a patient specimen for a prothrombin time.
Light blue-top tube containing a liquid anticoagulant, sodium citrate, is used for specimen collection from a patient for a prothrombin time test. (Daniels, 2009)
3) List two reasons for a patient to undergo PT testing.
i) To find cause for abnormal bleeding
ii) To measure the effectiveness of anticoagulant drug in anticoagulation therapy (McGlasson, 2003)
4) List which type of medication a patient might taking if the test were checked routinely.
Patients undergoing oral anticoagulation therapy (OAT) are required to test frequent PT/INR test. Drugs such as low molecular weight heparin and warfarin (Brand name - Coumadin) are popular anti-coagulatants. Frequent monitoring is required for two reasons: 1) to achieve the correct dosage; 2) to assess risk such as excessive bleeding, food-drug interaction, etc (McGlasson, 2003).
5) List at least five outside agents (foods, other medicines) that can affect a patient's blood viscosity and the effectiveness of anticoagulation therapy.
Some food items affecting blood viscosity are: Food high in vitamin K, example Spinach, brussels sprouts, cranberry juice, coffee, broccoli, animal protein such as liver, etc.
Some drugs affecting blood viscosity are: Theophylline, ranitidine, guanidine, Aspirin, salicylate, oral contraceptives, etc. (Daniels, 2009)
References
Daniels, R. (2009). Delmar's Manual of Laboratory and Diagnostic Tests: Organized by Type of Test. Cengage Learning. (p. 351)
McGlasson, D. L. (2003). Laboratory Variables That May Affect Test Results in Prothrombin Times (PT)/International Normalized Ratios (INR). Lab Medicine, 34(2), 124-129.
Poller L. (2004). International Normalized Ratios (INR): the first 20 years. J Thromb Haemost, 2: 849–860.
