Comparison of Point-of-Care PT-INR by Hand-Held Device with Conventional PT-INR Testing in Anti-phospholipid Antibody...

Evidence on agreement of point-of-care (POC) INR testing with laboratory testing in APS patients on oral anticoagulation (OAC), is scarce. This study assessed agreement of paired PT INR testing by a POC device vs. conventional platform-based laboratory test, in APS patients on OAC using a pre-determined definition of agreement. Simultaneous paired PT INR estimation in 92 APS patients was carried out, during October 2020-September 2021. POC INR was performed on capillary blood (pin prick) using the qLabs® PT-INR hand-held device, while laboratory INR estimation was performed using citrated blood (venepuncture) on STA-R Max Analyzer® using STA-NeoPTimal thromboplastin reagent®. Concordance was defined no greater than ± 30% (as per international standards ISO 17593:2007 guidelines) for each paired INR estimation. Agreement between the two was defined as ≥ 90% of paired INR measurements being concordant. 211 paired estimations were performed, within which 190 (90%) were concordant. Good correlation was seen between the 2 methods of INR estimation on Bland Altman plot analysis with an Intra-class correlation coefficient (95% CI) of 0.91(0.882, 0.932). Lab INR range > 4 (P = 0.001) was a significant predictor of higher variability between both methods of INR estimation. Lupus anti-coagulant, other anti-phospholipid antibodies (APL) or triple APL positivity did not result in any statistically significant variation in paired measurements. This study demonstrated good correlation between POC INR measurement and Lab INR estimation and agreement was ascertained between the 2 methods in APS patients on OAC.