A Comprehensive Clinical Assessment of the LumiraDx International Normalized Ratio (INR) Assay for Point-of-Care Monitoring in Anticoagulation Therapy.

BACKGROUND

The International Normalized Ratio (INR) monitors anticoagulant treatment but relies on laboratory-based services. This could limit access to rapid monitoring and increase the diagnostic delay, both of which may be addressed by point-of-care testing (POCT). This study investigated the LumiraDx POC platform for INR monitoring.

METHODS

INR was measured on recalcified residual venous ( = 94) specimens from Chris Hani Baragwanath Hospital and capillary blood specimens ( = 254) from consenting enrolled participants at Charlotte Maxeke Johannesburg Academic Hospital Anticoagulation clinic, Johannesburg, South Africa. Standard-of-care (SOC) INR was measured on sodium-citrated venous blood using the Sysmex-CS2500 platform (Siemens Healthcare) and Neoplastin-R (Roche Diagnostics and Diagnostica Stago, Paris, France) within 2 h post-venipuncture. Within run, precision was measured using 2 LumiraDx control levels. The statistical agreement of paired INR measurements was also stratified by dosing decision.

RESULTS

The precision was within the manufacturer's claim for controls (level 1%CV: 3.63, level 2%CV: 2.24). Accuracy analysis showed a moderate overall agreement compared to the SOC INR results with a correlation coefficient of 0.94 (95% Cl, (0.9267 to 0.9497)). The overall precision (ρ > 0.9) and accuracy (C = 0.9842) were good with an absolute bias of 0.07. The 95% confidence intervals for the slope and intercept did not include 1.00 and 0.00, respectively; however, the total calculated error was within the minimal acceptable limits.

CONCLUSION

The LumiraDx INR Test showed a good performance compared to laboratory-based testing and provided opportunity for rapid and patient-centric care. Owing to an increasing positive bias for INR > 3.5, confirmation with laboratory INR measurements may be required.