Evaluating commutability of EQA samples for epstein-barr virus serology

Abstract

Background: Providing ‘patient-like’ commutable samples is an ongoing challenge for all EQA providers. RCPAQAP sources human serum and plasma from commercial suppliers, donated de-identified pools and consenting donors. For some assays plasma is not the recommended specimen type for testing. Aim: In 2019, RCPAQAP performed plasma to serum conversion for EBV surveys previously distributed as a plasma sample to investigate the effect of sample type on results. Methods: A single source plasma sample (from Physicians Plasma Alliance collected in sodium citrate) was distributed for two EBV surveys. RCPAQAP subsequently performed a plasma to serum conversion using an in-house method and redistributed the defibrinated sample for a third survey. A comparison of the replicate samples was performed to identify any discrepancies. Results: A shift in reporting for qualitative results (positive/negative) for EBV VCA IgM was noted over the three surveys. The two surveys using plasma samples had less than 80% agreement across methods whereas a consensus of 90% was achieved for the defibrinated sample. Discussion: There are many contributing factors that can lead to variation in results including sample type. For serological testing, it is important to be aware of any limitations for the assay in use. RCPAQAP now routinely defibrinates plasmas where required to improve the commutability of the sample.