Point-of-care versus central laboratory testing of INR in acute stroke

Effective anticoagulant therapy is a contraindication to thrombolysis, which is an effective treatment of ischemic stroke if given within 4.5 hours of symptom onset. INR above 1.7 is generally considered a contraindication for thrombolysis. Rapid measurement of INR in warfarin-treated patients is therefore of major importance in order to be able to decide on thrombolysis or not. We asked whether INR measured on a point-of-care instrument would be as good as a central laboratory instrument.

A total of 529 consecutive patients who arrived at the emergency department at a large urban teaching hospital with stroke symptoms were enrolled in the study. INR was measured with a CoaguChek and a Sysmex instrument. Basic clinical information such as age, sex, and diagnosis (if available) was recorded. INR from the instruments was compared using linear regression and Bland-Altman plot.

Of 529 patients, 459 had INR results from both instruments. Among these, 3 patients were excluded as outliers. The rest (n = 456) showed good correlation between the methods (R²  = 0.97). In the current setting, CoaguChek was in median 63 minutes faster than Sysmex.

Our results indicate that point-of-care testing is a safe mean to rapidly acquire a patient's INR value in acute clinical situations.