Evaluation of the refractometric method for the determination of total protein in avian plasma or serum

Serum total protein concentrations in pigeon blood determined with the biuret method (TPB-se) were compared with total protein concentrations in plasma (TPR-pl) and serum (TPR-se) obtained by estimation from refractive index. The refractometric method consistently yielded higher values (P<0.01). A significant correlation between TPB-se and TPR-se was found (r = 0.62) but not between TPB-se and TPR-pl. The calculated regression equation TPR-se = 0.69 TPB-se + 16 was considered to have no practical value, because the correlation coefficient was low (r = 0.62). The refractometric method for determination of TP in pigeon blood is not recommended.