Effect of anticoagulants and glucose on refractometric estimation of protein in canine and rabbit plasma

The effect of ethylenediaminetetraacetate (EDTA) compounds on the refractometric estimation of plasma protein concentration was attributed largely to osmotic fluid shifts, as reflected in changes in hematocrit, and to addition of total solids to the plasma. With H4EDTA, these two mechanisms were additive and caused increased plasma protein readings of significant magnitude even at recommended (1--2 mg/ml) anticoagulant concentrations. For the potassium and sodium salts, the two mechanisms were partly compensatory, which ameliorated the effect at 1--2 mg/ml concentration. At higher concentrations, such as might occur if a blood collecting tube were incompletely filled, all of the EDTA compounds caused technically significant over-estimation of plasma protein. When dextrose (d-glucose) was added in-vitro to canine blood, in amounts analogous to clinical hyperglycemia, the effect upon plasma protein estimation was minimal.