CAP Laboratory Improvement Programs Laboratory Reporting of the International Normalized Ratio Progress and Problems

● Context.—The international normalized ratio (INR) is widely used to monitor oral anticoagulation and to evalu-ate patients with coagulation disorders. Objective.—To examine the variability of the perfor-mance and reporting of the INR and to evaluate laboratory calculation of the INR. Design.—Between 1993 and 2003, laboratories partici-pating in proficiency testing were surveyed. Participants provided the international sensitivity index and the mean normal prothrombin time used to calculate the INR. The INR was calculated from the data provided and compared with the INR reported to determine if the calculation was correct. Results.—Survey data regarding the INR collected be-tween 1993 and 2003 demonstrate an improvement in re