PB1085 - Laboratory versus point-of-care INR testing in patients with lupus anticoagulant – a retrospective cohort analysis

Background: Patient self-testing (PST) and self-management (PSM) using point-of-care (POC) devices, was found to improve the quality of anticoagulation, reduce thromboembolic events and all-cause mortality, and is recommended for VKA monitoring by various guidelines. Accumulated evidence supports the accuracy of LAC insensitive thromboplastins for INR testing in patients with lupus anticoagulant (LAC), however this may not be generalized for patients monitored by POC devices

Aims: To investigate the accuracy of POC devices for measuring INR in LAC positive and negative patient cohort followed at our outpatient clinic

Methods: We retrospectively analyzed INR results of consecutive VKA treated patients (with and without evidence of LAC in repeated testing) followed at our clinic and having had their INR checked simultaneously by both POC device (CoaguChek® XS) and our laboratory. We used linear models and analysis of covariance to evaluate the correlation between INR results from the POC device versus laboratory INR in adjusting for the presence of LAC

Results: We identified 510 paired samples from 130 patients of which 56 (43%) were LAC positive treated with VKAs mainly for venous and arterial thrombosis with a median age of 44 years. The ANCOVA full model analysis showed a very good correlation between INR results obtained by the POC device and laboratory INR results in both LAC negative and LAC positive patients (figure). The presence of LAC had no effect in the model on the correlation between POC and lab INRs (p=0.378) while the POC INR results had a very significant effect (p < 0.001) and explained 79% of the variance in lab INR results

Conclusion(s): The correlation between INR results obtained by the POC device and the laboratory was comparable for both LAC positive and negative patients, suggesting POC devices may be used for PST and PSM regardless of LAC status