How should blood rheology be measured in macroglobulinaemia?

Blood and plasma viscosity were measured in 13 patients with monoclonal mac roglobulinaemia. Blood viscosity was measured at natural hematocrit and aft er adjustment to 45%. Studies were performed at three different temperature s, +24 degrees C, +32 degrees C and +37 degrees C. Plasma viscosity was mea sured in a rotational viscometer and in a capillary tube at the above-menti oned temperatures. Blood viscosity was to some extent related to the patien ts' symptoms, whereas a correlation between blood and plasma viscosity beca me less pronounced with decreasing shear rates, indicating that plasma visc osity is not a perfect indicator of blood viscosity in macroglobulinaemia. It was shown that red cell concentration, besides the concentration of mono clonal immunoglobulins (=paraproteins (PP)), is an important determinant of blood viscosity. The correlation between red cell concentration and viscos ity became stronger with decreasing shear rate. Whole blood viscosity at lo w shear rates seems to be the best indicator of rheological symptoms in pat ients with macroglobulinaemia. It is concluded that blood rheology in patie nts with macroglobulinaemia is best studied at +32 degrees C to +37 degrees C in whole blood and at low shear rates.