Accuracy of CoaguChek XS for Point-of-Care Antithrombotic Monitoring in Children with Heart Disease

The CoaguChek XS international normalized ratio (INR) assay was compared to INR assay by a standard laboratory method in children with heart disease on anticoagulant therapy. The data comprised 120 pairs of INR values for 42 patients (age <16 yr) who attended a cardiology clinic between 1 May 2007 and 30 January 2008. Parallel INR assays by the CoaguChek XS and the standard method were performed within 1 hr by a single qualified technician and the paired results were evaluated by linear regression and Bland-Altman analysis. The mean difference in the INR values was -0.08 +/- 0.04 units (p = 0.63); the difference between the two results was consistently <0.5 INR units. The slope of the regression line was 0.98 (95% CI: 0.96 to 1.01) and the y-intercept was 0.014 (95% CI: -0.01 to 0.04). In the Bland-Altman analysis, the mean difference in INR between the two methods was 0.08 units and values for 99.4% of the patients fell within the limit of agreement (-0.17 to 0.28 units). In summary, INR assays in children by the CoaguChek XS device are as accurate as the standard method, but faster and more convenient.