POCT PT INR — Is it adequate for patient care? A comparison of the Roche Coaguchek XS vs. Stago Star vs. Siemens BCS in patients routinely seen in an anticoagulation clinic

Background In this study we examined the difference in patient INR values as measured by the POCT CoaguChek XS device and central laboratory Stago Evolution and Siemens BCS XP analyzers. Methods This study composed of 100 warfarin therapy patients and 20 coagulation normal subjects, showed that the difference between the POCT and clinical laboratory values increased with increasing INR and was exacerbated by the use of different thromboplastin reagents by the POCT and central lab. Results The CoaguChek XS and on-site Stago analyzers which used human recombinant (ISI = 1.01) and rabbit brain thromboplastin (ISI = 1.25), respectively, showed reasonable agreement for INR < 3.0 (k = 0.62) but significant difference for INR ≥ 3.0 (k = 0.10). In contrast, the CoaguChek XS and Siemens BCS XP, which both employed human recombinant thromboplastin (BCS ISI = 1.02), showed greater agreement for the complete range INR values (INR < 3.0 k = 0.84; INR ≥ 3.0 k = 0.70). ECAA Poller calibrant data showed the automated instruments were performing as expected, indicating that ISI calibrations were correct but insufficient to standardize the INR values for the different thromboplastin methods across the full range of measured INRs. Central lab verification of POCT INR > 5.0 with the Stago Evolution prevented adverse treatment events for the warfarin therapy patients in the six months preceding and following this investigation.