An evaluation of the performance of blood gas analysis in the UK using tonometered haemolysate material

Abstract

WEQAS is one of the largest and the most rapidly expanding national EQA Schemes in the UK with over 500 participants. Since April 1995, the Scheme has distributed a tonometered protein-based aqueous material for blood gas analytes (H+, pCO2, pO2), electrolytes, glucose and lactate. Current performance of the new generation of blood gas analysers show marked bias between analysers which a number of manufacturers have attributed to a “matrix” effect. This study was undertaken to investigate the “true” analytical performance of these analysers utilising a tonometered haemolysate blood product with oxygen saturation kinetics identical to that of fresh blood. One hundred laboratories that represented the major analyzers used in the UK were selected to participate in the study. Participants were asked to analyse the samples within 1 week of tonometry of the material. Performance data, expressed as interlaboratory variation, was compared with concentration matched data from the same group using the aqueous material. Significant improvement in instrument Bias was observed for the AVL Omni and iStat analysers for pO2. Surprisingly, there was also an improvement in bias for the electrolyte parameters on the IL synthesis. However, a significant positive bias was observed for the AVL Opti for Potassium and for the Nova analyzer for glucose using this material. Similar performance was observed for the co-oximetry, parametres for fresh and lyophilised material for the majority of analyzers.