Prothrombin Time Standardization: Proposal of the Standards Committee, College of American Pathologists, Subcommittee on Coagulation Reagents

Standard plasmas having a known concentration of the coagulation factors determining the one-stage prothrombin time are evaluated from the standpoint of factor assays, stability, and reproducibility. The problem of standardizing the one-stage test and commercial thromboplastins is reviewed, and it is proposed that these plasma standards be used for that purpose.