What problems might one encounter performing a biuret test for protein on intact red blood cells?

This test is based on the interaction between the copper ions of the Biuret reagent and the amino groups of the peptide bonds of the amino acids that make up proteins. When there is a reaction, the color changes blue to violet.

Due to it is not very sensitive compared to the lowry method and requires 2 to 4mg of protein per test, opalescence may occur if the sample has high levels of lipids and carbohydrates.