Comparison of four methods for determination of total protein concentrations in pleural and peritoneal fluid from dogs

Objective-To compare 4 techniques for determination of total protein concen trations in peritoneal and pleural effusions from dogs. Sample Popuiatlon-23 peritoneal and 12 pleural fluid samples from 35 dogs w ith various abnormalities. Procedure-Samples were collected into tubes containing EDTA, centrifuged, a nd stored at -20 C until total protein concentrations were assessed. Protei n concentration in each sample was determined by use of urine test strips, refractometry, and Bradford and biuret techniques. Accuracy of each method was determined, using dilutions of human control sera. Results-There was good correlation among results of all quantitative proced ures. Results of the biuret technique were more accurate than results of th e Bradford assay. Refractometry underestimated protein concentration in sam ples with < 20 g of protein/L. Results of urine test strips correctly class ified effusion samples into 2 groups on the basis of total protein concentr ations less than or greater than 20 g/L. Conclusions and Clinical Relevance-Results of any of these 4 techniques can be used to rapidly and efficiently differentiate peritoneal and pleural fl uid from dogs into transudates and exudates on the basis of total protein c oncentration less than or greater than 20 g/L, respectively.