Comparison between international normalized ratio using a portable device and conventional methodology

OBJECTIVE: to compare the international normalized ratio (INR) measured by a point-of-care (POC) testing device with that measured by the conventional method in patients undergoing anticoagulation therapy with warfarin sodium. METHODS: The INR of 383 warfarin-treated patients (mean age: 56.5 years; 207 female) was measured in capillary blood using the Hemochron Jr. device and compared with that of venous plasma samples determined by the conventional method performed in a Coag-A-Mate analyzer. Results were evaluated globally and for the following subgroups: INR 3.5. RESULTS: Using both methods, the comparison between INR values yielded a correlation coefficient (r) of 0.86. However, mean differences in INR in both tests, considering the three subgroups, proved to be statistically significant (p <0.001): 0.14 ± 0.21 (INR< 2.0); 0.54 ± 0.31 (2.0 < INR 3.5). Paired Student’s t-test analysis revealed a p value < 0.001 for the three subgroups studied. CONCLUSION: The use of point-of-care testing for monitoring oral anticoagulation has some limitations. Anticoagulation intensity was underestimated by this method in the three subgroups studied.