Analytical validation of commercial assays for the determination of haptoglobin, C-reactive protein and serum amyloid A in dogs

All laboratory tests must be validated before being introduced for patient testing. The objective of this work was to perform the analytical validation of three commercial assays that are being used at our laboratory for the determination of haptoglobin (Hp), C reactive protein (CRP) and serum amyloid A (SAA) in canine samples with low and high concentrations of these acute phase proteins (APPs). The parameters evaluated for the validation of the methods were: (1) Precision, assessed by determination of the within and between-run coefficients of variation (CVs). (2) Inaccuracy, evaluated indirectly by investigating linearity under dilution. (3) Limit of detection, determined as the lowest concentration of the APPs which could be distinguished from a zero sample. All within-run CVs were lower than 10%, however between-run CVs were lower than 10% only for Hp. Dilution of a serum sample with high concentrations of the different APPs resulted in a linear regression equation with correlation coefficient R-2 > 0.98 in all cases; so all methods showed a good accuracy. The detection limit of each assay was 0.02 g/L for Hp, 0.15 mg/L for CRP and 0.79 mg/L for SAA. Additionally they differentiate animals with inflammatory or infectious diseases from healthy subjects. Overall results of validation showed that the assays tested can be suitable for the routine measurement of APPs in canine samples, although it would be desirable to reduce the between run imprecision found for CRP and SAA assays.