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

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Acute stroke is a serious medical condition with potentially devastating outcome. Almost 17 million people suffer a stroke globally every year,1 25 000 of which in Sweden.2 Neuroimaging with computer tomography can distinguish between ischemic or hemorrhagic stroke. Ischemic stroke can be treated with thrombolysis when no contraindications are present and the treatment can be started within 4.5 hours of symptom onset.3 One contraindication of thrombolysis is effective, ongoing anticoagulant treatment. In patients treated with warfarin, an INR above 1.7 has been used to indicate this.4 Furthermore, in patients with intracerebral hemorrhage, knowledge of an elevated INR may allow early reversal of warfarin effect.6
Measurement of INR in central laboratories is accurate but time‐consuming. Point‐of‐care testing of INR versus central laboratory measurements has previously been investigated. In spite of several studies about this issue,7 whether CoaguChek can be used as an acute mean to rapidly acquire a patient's INR value is still not clear. Results are somewhat contradictory with some studies suggesting a good correlation7 while others on the contrary imply that an INR measured on a point‐of‐care instrument does not correlate well to central laboratory instruments.12 Most of the studies are also of small cohort sizes. To the best of our knowledge, no large study clearly recommends the use of CoaguChek in acute settings. Therefore, several national recommendations practically limit the use of CoaguChek in acute settings, insisting on parallel analysis on a central laboratory instrument on at least two occasions for each new patient before CoaguChek value can be trusted and to avoid potential discrepancies.
Swedish Society on Thrombosis and Haemostasis’ recommendation on the use of point‐of‐care testing instruments for analysis of INR suggests that before definitive start of use of point‐of‐care testing instruments for patients on anti‐vitamin K treatment, they should be tested with both capillary sampling on the point‐of‐care testing instrument and venous sampling in the local central laboratory at two occasions.14 This makes use of point‐of‐care testing instruments in acute situations practically impossible for unknown newly admitted patients as most of the patients at the emergency department are. To change the recommendations, a new large study addressing this issue is therefore needed.

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