Evaluation of an in-clinic dry chemistry analyzer for canine, equine, and feline plasma samples

Method validation studies characterize the performance of new laboratory methods relative to established methods using quality guidelines in order to define the new method's performance characteristics and to identify differences that could influence data interpretation. We investigated the performance of an in-clinic dry chemistry analyzer (Catalyst One, IDEXX) for measuring 19 routine plasma biochemistry analytes in dogs, cats, and horses. We analyzed 2 levels of quality control material (QCM) in duplicate twice daily for 5 d to determine the coefficient of variation (CV), percent bias, observed total error (TEobs), and sigma metric (sigma) for each analyte at each level of QCM. We analyzed 82 canine, equine, and feline plasma samples with the in-clinic dry chemistry analyzer and a reference wet chemistry analyzer, and results were compared using correlation coefficients, Deming regression, and Bland-Altman analyses. CVs were <5% for 16 analytes and > 5% for 3 analytes. TEobs was less than allowable total error (TEa) for 9 analytes, and exceeded TEa for 10 analytes. Sigma metrics were >4 at both levels of QCM for 5 analytes, and at one level of QCM for 5 analytes; sigma metrics were <3 or could not be calculated at the remaining analyte concentrations. All analytes, except glucose, showed various magnitudes of bias compared to the wet chemistry analyzer. Based on these results, we recommend statistical (5 analytes) and non-statistical (14 analytes) QC measures and analyzer-specific reference intervals.