ABSTRACT
Plasma viscosity is a useful screening test for the presence of organic disease and a sensitive monitor of disease activity. It is also useful in specific diagnosis of paraproteinemias, in which it can be used to predict the clinical plasma hyperviscosity syndrome. Whole blood viscosity has little use in routine clinical diagnosis. Since it is a global measurement, which is affected by red cell characteristics as well as by plasma protein changes, it is less sensitive to plasma protein changes in disease than plasma viscosity or erythrocyte sedimentation rate. The viscosity of a liquid is its resistance to flow, due to internal friction between molecules and other particles. Plasma and serum viscosity depend principally on the plasma protein pattern and the temperature: they are independent of the shear rate, with the rare exceptions of some paraproteinemic plasmas and sera. Plasma is a suspension of proteins and smaller molecules in water.
