The changing face of activated protein C resistance testing—a 10-year retrospective
Elysse Dean, Emmanuel J. Favaloro
Abstract
Abstract: Activated protein C resistance (APCR) is a hypercoagulable condition that increases the risk of venous thrombosis. The Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) offers external quality assessment testing for APCR twice a year. Participants either used activated partial thromboplastin time (APTT) or Russell viper venom time (RVVT) based methods to perform clotting assays, with the endpoint being identification or exclusion of APCR. We aim to identify trends including which methods and reagent kits perform better in the identification of APCR vs. those reagent kits with increased risk of reporting false positives and/or false negatives. Data using 40 samples sent to RCPAQAP participants over the past 10 years was analysed. False positive and false negative rates were calculated per sample, and reagent kit. There was an 18% increase in participants performing APCR testing over the 10 years, with participants reporting fewer incorrect interpretations in 2019 (3.0%) compared to 2010 (16.8%). This was coincident with a move from APTT to RVVT based methods, with 59% users of RVVT methods in 2019, compared to 48% in 2010. This change likely contributed to lower percentages of incorrect results, as it was found that participants using APTT based assays reported more false negatives (87.8% of total) and false positives (72.2% of total) than those using RVVT based assays.