By how much are plasma levels of total protein higher than serum levels?

Plasma levels of total protein are generally higher than serum levels due to the presence of fibrinogen and other clotting factors in plasma that are not present in serum. When blood is allowed to clot, these proteins are removed along with the clot, leading to a decrease in the total protein measurement. The typical difference between plasma and serum total protein is commonly acknowledged to fall within the range of 0.2-0.4 g/dL. This is attributed to the quantitative contributions of fibrinogen and other soluble clotting factors found in plasma.

In the context of the choices provided, selecting the interval of 0.2-0.4 g/dL accurately reflects the established understanding of protein levels in serum versus plasma, aligning with the physiological role of clotting factors and the procedures used to obtain these samples. Other ranges may overestimate the expected difference, as they do not conform to the general clinical observations regarding total protein concentrations in these two types of samples.