Generational performance of three point-of-care testing devices compared with standard laboratory measurement of the international normalised ratio across extended ranges

Correspondence to Dr Hui Ming Tay, Department of Hematology, Singapore General Hospital, Singapore 169856, Singapore; tay.hui.ming@singhealth.com.sg Introduction Point-of-care testing (POCT) of the international normalised ratio (INR) is recognised as a rapid and reliable alternative to venous INR measurement for titration and monitoring of patients anticoagulated with vitamin K antagonists.1–4 Besides empowering patient self-testing and self-management,5–7 POCT coagulometers are now widely used in healthcare institutions for bedside anticoagulation management and have replaced venous INR sampling in many anticoagulation clinics (ACCs).8–10 For the past decade, our institution has been using the CoaguChek XS system (Roche Diagnostics, Basel, Switzerland) for INR testing at our outpatient ACC and inpatient anticoagulation service. INR measurements on the POCT meters are based on electrochemical measurement using disposable test strips containing a recombinant human thromboplastin and a peptide substrate which combines with patient capillary blood samples to initiate the reaction. For the sample size calculation, an estimated Pearson correlation effect size of r=0.9 was used based on findings from our previous studies with a tolerable CI of ±0.1. [...]the CoaguChek system has consistently demonstrated its excellent performance at lower INR ranges with improvement at higher INRs in its latest iteration intended for professional use.