History
The prothrombin time was discovered by Dr Armand Quick and colleagues in 1935, and a second method was published by Dr Paul Owren, also called the "p and p" or "prothrombin and proconvertin" method. It aided in the identification of the anticoagulants dicumarol and warfarin, and was used subsequently as a measure of activity for warfarin when used therapeutically.
The INR was introduced in the early 1980s, by Dr. Jack Hirsh and colleagues at McMaster University School of Medicine, when it turned out that there was a large degree of variation between the various prothrombin time assays, a discrepancy mainly due to problems with the purity of the thromboplastin (tissue factor) concentrate. The INR became widely accepted worldwide, especially after endorsement by the World Health Organization.
Read more about this topic: Prothrombin Time
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