International Normalized Ratio
The International Normalized Ratio (INR) is a "system established by the World Health Organization and the International Committee on Thrombosis and Hemostasis for monitoring and reporting blood coagulation tests. Under this system, results are standardized using the International Sensitivity Index for the particular test reagent/instrument combination used.
Point-of-care testing of the INR with a sample of blood obtained by fingerstick may or may not be as reliable as an INR measured by a central laboratory. Clinical practice guidelines by the American College of Chest Physicians state "where possible, we suggest that personnel using POC office-based testing participate in proficiency schemes available through professional or national quality assurance organizations".
The CoaguChek system may be more accurate than other POC systems and allows recalibration. However, laboratories vary in the performance when using the CoaguChek. External quality assessment is recommended of the CoaguChek.
Self-monitoring of INRs by patients
"Compared to standard monitoring, patients who self-monitor or self-manage can improve the quality of their oral anticoagulation therapy. The number of thromboembolic events and mortality were decreased without increases in harms. However, self-monitoring or self-management were not feasible for up to half of the patients requiring anticoagulant therapy. Reasons included patient refusal, exclusion by their general practitioner, and inability to complete training" according to a meta-analysis by the Cochrane Collaboration. 
- Anonymous (2019), International Normalized Ratio (English). Medical Subject Headings. U.S. National Library of Medicine.
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