Commutability of external quality assessment materials for point-of-care glucose testing using the Clinical and Laboratory Standards Institute and International Federation of Clinical Chemistry approaches

Objectives: The aim of this study was to assess the commutability of three external quality assessment (EQA) materials for point-of-care (POC) glucose testing using two approaches, to identify suitable EQA materials to evaluate and monitor the quality of POC testing. Methods: Commercial control materials (CCMs), pooled human serum samples (PHSs), and homemade human whole-blood samples (HWBs) were measured along with 33 individual clinical samples using five POC instruments and a Hitachi 7600 analyzer. Data were analyzed by Deming regression analysis with a 95% prediction interval as described in Clinical and Laboratory Standards Institute (CLSI) EP30-A, and by difference in bias analysis as described by the International Federation of Clinical Chemistry (IFCC) Working Group on Commutability. Results: Using the CLSI approach, HWBs, CCMs, and PHSs were commutable with five, one, and two instruments, respectively. With the IFCC approach, HWBs were commutable with two instruments, while CCMs and PHSs were largely inconclusive or non-commutable on five instruments. Conclusions: HWBs were commutable on all instruments by the CLSI approach and may be a suitable EQA material for POC testing. Although some results differed between the IFCC and CLSI approaches, both indicated that HWBs were far superior to CCMs and PHSs in commutability.