![]() ![]() Baseline sample collection before starting anticoagulation.Disseminated intravascular coagulation (DIC).Bleeding diathesis in patients with coagulation factors deficiency (fibrinogen and factors II, V, VII, or X, or a combined deficiency) in the extrinsic pathway.The indications for obtaining an INR value are: The INR value from POCT is considered acceptable if it does not exceed plus or minus 0.5 INR units by the reference laboratory INR value. On the other hand, capillary whole blood can be obtained from POC-PT systems by a fingerstick which is then applied to a test strip or cartridge. ![]() Providers should be vigilant if the specimen is taken from a vascular-assisted device because there may be possible heparin contamination that may interfere with INR reliability. The total time between sample collection and testing should not exceed 24 hours. The tube should be then inverted a few times, gently and as soon as possible, for proper mixing with the anticoagulant. The tubes must be filled to within 90% of the full collection volume. The acceptable anticoagulant is the concentration of sodium citrate 3.2%. It is recommended by the Clinical and Laboratory Standard Institutes (2017) that the blood specimens for INR/PT testing in the laboratory setting should be collected from venous blood and it is directly obtained into a tube with a light blue top. In additon, apart from adherence and treatment satisfaction some patient found to be more anxious about the PT/INR monitoring. Patient with antiphospholipid antibodies have been found to have higher error rate in INR determination. However, POC devices tend to overestimate low INR values and underestimate high INR values. Potential advantages of POC devices include improved convenience to patients, better treatment adherence, frequent measurement and fewer thromboembolic and bleeding complications. It can be performed at or near the patients with the advantage of shorter turnaround time and improved clinical outcome. POC devices are used in practitioner offices, long-term care facilities, pharmacies, or for patient self-testing or self-management. However, given the higher CCT turnaround time including collection, transportation, and processing of blood samples, Point-of-care coagulation test (POCT) also known as “bedside testing” or “near-patient testing" has been developed. Specimen CollectionĬonventional coagulation testing (CCT) can be performed in the laboratory setting to measure PT/INR. Optimizing the patient’s INR therapeutic range can be challenging as narrow therapeutic range had been seen in VKAs and can be affected by patient's characteristics, co-morbid conditions, diet, and other drug interactions. Patients are monitored every 3–4 weeks or less at the thrombosis centers (TC), point-of-care (POC) clinics, or in the home setting. INR value is dimensionless and ranges from a score of 2.0 to 3.0. The reference values for INR take into account in PT measurement in device related variations, type of reagents used, and sensitivity differences in the TF activator. PT, the time in seconds, is measured in plasma to form a clot in the presence of sufficient concentration of calcium and tissue thromboplastin by activating coagulation via the extrinsic pathway. The INR is derived from prothrombin time (PT) which is calculated as a ratio of the patient’s PT to a control PT standardized for the potency of the thromboplastin reagent developed by the World Health Organization (WHO) using the following formula: Patients taking oral anticoagulants are required to monitor INR to adjust the VKA doses because these vary between patients. It can also be used to assess the risk of bleeding or the coagulation status of the patients. International normalized ratio (INR) is the preferred test of choice for patients taking vitamin K antagonists (VKA). ![]()
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