Point of Care INR testing devices: performance of the Roche CoaguChek XS and XS Plus in the UK NEQAS BC external quality assessment programme for healthcare professionals: four years’ experience

Background Vitamin K antagonists have been used for many decades and have been traditionally monitored by the measurement of the International Normalised Ratio (INR) in the laboratory. Introduction of Point of Care (POC) testing devices to measure INR has resulted in many tests being undertaken in primary care. External Quality Assessment (EQA) of these POC devices is recommended to ensure accuracy and reliability of INR results outside a laboratory setting. Aim To assess the quality of INR results for users of two POC devices (CoaguChek XS and CoaguChek XS Plus) over a four-year period. Methods Four surveys (two samples) were sent in each 12-month period. The median INR value of each sample was calculated and the percentage deviation from this median determined. Any results greater than 15% from the median were considered to be outside consensus which indicated a possible problem within the testing system. Results Variability of INR results in this UK National External Quality Assessment Scheme (NEQAS) programme was comparable to that in the UK NEQAS EQA programme for laboratory INR testing. Occurrence of persistent problems was lower in the POC programme than the laboratory programme. Conclusions Utilisation of an EQA programme for POC devices in primary care is feasible and necessary. Our data suggest for those health professionals using EQA, the reliability and accuracy of INR testing matches the quality of laboratory testing.