Interference by cryoglobulins with white blood cell measurements on Coulter Counter

By using the Coulter Counter S-Plus IV erroneous measurements of leukocytes, platelets and red cells were experienced in blood from two patients with cryoglobulinaemia. Leukocyte levels were estimated too high owing to contamination of the leukocyte counting chamber by unlysed erythrocytes. One of the patients had leukopenia, but the Coulter Counter reported white blood cell counts within normal limits. Rewarming of the sample to 37 degrees C eliminated the problem.