Analytical Performance Evaluation of the New GEM® Premier™ 5000 in Comparison to the Epoc® Blood Gas Analyzer in Horses

Blood gas analyzers are stationary or hand-held machines used to measure blood gases and electrolytes in a blood sample taken from a patient. No machine has been specifically designed for use in horses, and therefore every machine needs to be validated before being used in equine practice. The aim of this study was to compare the newly marketed GEM5000 machine to the formerly validated epoc machine for blood gas analysis in horses. Blood samples taken from healthy and sick horses were run on both machines in alternate order, and various statistical tests were used to analyze if the two machines give similar results. Although the precision of the GEM5000 is good for most parameters, the agreement with the epoc machine is not always satisfactory. Therefore, data from different blood gas machines should not be used interchangeably. Different blood gas analyzers are used in equine practice. Every machine needs to be validated, as they have not been designed for use in horses. The aim of this study was to compare the newly marketed GEM5000 machine to the formerly validated epoc machine for blood gas analysis in horses. In this prospective, non-blinded, comparative laboratory analyzer study, 43 equine blood samples were analyzed on both analyzers and values were compared between the two machines via Lin's concordance analysis, Passing-Bablok regression analysis and Bland-Altman plots. Duplicate measurements were conducted on the GEM5000 machine to evaluate precision. The GEM5000 failed to achieve the required precision for tHb, Hct and iCa(2+), but achieved acceptable precision for all other parameters. Concordance correlation analysis revealed poor correlation for Na+, Cl-, iCa(2+), K+, Hct and tHb, while there was an at least moderate agreement for all other parameters. Passing-Bablok regression revealed significant constant bias for pCO(2), pO(2), Cl-, and iCa(2+) and significant proportional bias for pCO(2), iCa(2+) and SO2. Bland-Altman analysis revealed significant systematic bias for Na+, Cl-, iCa(2+), K+, Hct, tHb and SO2. This study shows that while precision of the GEM5000 is good, values should not be used interchangeably with data obtained from other blood gas analyzers.