Efficacy of Point-of-Care for INR Testing Compared to Standard Laboratory Methods at a Tertiary Care Hospital in Saudi Arabia.

Abstract

Regular testing of the international normalized ratio (INR) is essential for people taking vitamin K antagonists as part of anticoagulation therapy. This study was undertaken to ascertain the efficacy of point-of-care testing (POCT)-INR versus conventional core laboratory testing in terms of result adequacy, waiting-time reduction, and patient satisfaction enhancement at the thrombosis clinic of the outpatient Medical Specialties Department in King Fahad Medical City, Saudi Arabia. The study was conducted prospectively for 6 months (from June 2017 to December 2017) on 182 eligible participants out of 250 entitled patients who were attending the thrombosis clinic for warfarin dose adjustment and who fulfilled all the prerequisites for performing dual testing by fingerstick at the clinic and venipuncture by the core laboratory. The data-capturing template created on Microsoft Excel recorded turnaround times (TATs), clinical concordance of INR result variables by POCT, and laboratory methods. Individual patient experience was recorded to gauge satisfaction rate, and all the data were analyzed statistically. Of 182 patients included in the study, overall good concord was observed between POCT whole blood and laboratory plasma INR results with median bias of 0.07 and 92.3% agreement using acceptability criteria for clinical concordance of Clinical Laboratory Standards Institute (CLSI) 14-A and International Standards Organization (ISO) 17593-2007, respectively. Marked improvement in terms of patient's time spent at the clinic was noted, with substantial reduction from 180 to ∼30 minutes (p < 0.001). Survey questionnaire responses indicated that POCT of INR was highly convenient and enhanced patient experience in terms of shorter wait time, minimal invasive procedures, and immediate result availability (p < 0.001). Predominantly, participants (75.4%) endorsed and expressed a strong preference for the POCT procedure over conventional laboratory testing. Whole blood INR testing for warfarin dose adjustment with validated POCT devices is adequately comparable to the core laboratory results. It also simplifies workflow steps at the thrombosis clinic, enhancing patient experience and convenience via the immediate availability of results, a less invasive procedure, and a marked reduction in waiting time. However, caution is needed with regard to higher INR results (≥4.7), which call for core laboratory confirmation.