The accuracy and precision of a portable refractometer in measuring the plasma total protein concentrations in Nigerian trade cattle

This study aimed to obtain the accuracy and precision of a refractometer compared to the biuret methods in measuring plasma total protein in cattle. The total protein concentrations were determined in 131 cattle plasma samples using the biuret and refractometry methods. Paired samples t-test values, Passing-Bablok regression equations and Bland-Altman plots were generated following statistical analysis of the total protein values. Statistical analysis revealed that the refractometer produced a significantly (P < 0.05) higher mean total protein value than the biuret method. The statistical precision and accuracy were 97.16% and 97.52%, respectively. The concordance correlation coefficient test (0.9476) showed a strong linear relationship between the total protein values obtained by the two methods and a moderate agreement between the two methods of total protein determination, but based on the Passing- Bablok analysis, both methods can be used independently. Furthermore, the CUSUM test for linearity with a large P of 0.10 also indicated a linear relationship between the two methods. The Bland-Altman plot indicated an analytical error of 3.0% which is clinically insignificant. The refractometry method was accurate with high precision for the determination of plasma total protein concentrations in cattle. It is portable, accurate and cost-effective.