Increased whole blood viscosity on cooling in a patient with cold hemoagglutinin disease.

The whole blood and plasma viscosities have been evaluated in a patient with cold hemoagglutinin disease at different temperatures and at different shear rates. At 37 and 42 degrees C, whole blood viscosity values, regardless of the shear rate applied, resulted to be correspondent to the hematocrit value (31%). The values observed were similar to those noted in a patient with chronic bleeding anemia and an approximately equivalent hematocrit (33%). The same was true for plasma viscosity. At 32 degrees C, whole blood viscosity, regardless of the shear rate, resulted to be higher than expected. The values observed were similar to those noted in a normal subject with a clearly higher hematocrit value (44%) and definitely higher than those noted in the chronic anemia patient. On the contrary, plasma viscosity remained unchanged. These studies indicate that in cold hemoagglutinin disease, red cell aggregation and piling are capable of increasing blood viscosity.