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C-reactive protein (CRP) is a major acute phase protein in both people and dogs.
The objective of this study was to evaluate the precision and accuracy of 3 different point-of-care tests (POCT) for canine CRP (cCRP) in comparison to a standard ELISA test, and to assess storage stability.
Blood samples were collected from 125 dogs (23 healthy and 102 diseased). Serum cCRP measurements were performed using the TECOmedical AG, the EUROLyser Diagnostica, and the LifeAssays POCT. The TECOmedical AG ELISA validated for canine serum was used as a reference method. Statistical analyses included descriptive statistics, inter assay variance for each POCT, comparison of results from each POCT with the ELISA using Spearman's correlation and Bland-Altman plots, and a t-test to evaluate sample stability.
ELISA cCRP values ranged from 0.1-4.7 mg/L (median 1.3) in healthy dogs and from 0-282 mg/L (median 17.3) in diseased dogs. Spearman's correlation coefficient between ELISA and the respective POCT measurements for cCRP concentration was 0.89 for TECOmedical, 0.85 for EUROLyser, and 0.97 for LifeAssays. Bias calculated from Bland-Altman difference plots was 27.6% for TECOmedical, -14.2% for EUROLyser, and -15.7% for LifeAssays. Inter assay reliability was > 0.9 for all POCT. Total observed error of the EUROLyser was 28.2% and therefore met the acceptable total error of 29.6%.
All POCTs were able to measure cCRP, but precision, accuracy, and correlation coefficients varied among the 3 systems. Therefore, serial measurements for monitoring of cCRP in dogs should always be performed using the same POCT system.