Commutability of a whole-blood external quality assessment material for point-of-care C-reactive protein, glucose, and hemoglobin testing

Abstract

BACKGROUND: The optimal situation in external quality assessment (EQA) is to use commutable materials. No previous study has examined the commutability of a whole-blood material for point-of-care (POC) testing. The aim of this study was to determine the commutability of the Norwegian Quality Improvement of Laboratory Examinations (Noklus) organization's “in-house” whole-blood EQA material for C-reactive protein (CRP), glucose, and hemoglobin for frequently used POC instruments in Norway and to determine the possibility of using a common target value for each analyte. METHODS: The study was performed according to the Clinical and Laboratory Standards Institute guidelines. The EQA material was pooled stabilized EDTA venous whole-blood containing different concentrations of the analytes. The EQA material and native routine patient samples were analyzed using 17 POC and 3 hospital instruments. The commutability was assessed using Deming regression analysis with 95% prediction intervals for each instrument comparison. RESULTS: The EQA material was commutable for all CRP and hemoglobin POC instruments, whereas for glucose the material was commutable for all POC instruments at the lowest concentration analyzed [126.0 mg/dL (7.0 mmol/L)] and for 3 POC instruments at all of the concentrations analyzed. CONCLUSIONS: Noklus EQA participants using CRP and hemoglobin POC instruments now receive results that are compared with a reference target value, whereas the results for participants using glucose POC instruments are still compared with method-specific target values. Systematic deviations from a reference target value for the commutable glucose POC instruments can be calculated, and this additional information can now be offered to these participants and to the manufacturers.