Inefficacy of plasma exchange in cold agglutinin hemolytic anemia--a case study.

A therapeutic trial of plasma exchange was conducted in an 82-year-old woman with severe cold agglutinin hemolytic anemia, who was unresponsive to conventional treatment. In spite of considerable improvement of pertinent parameters (total IgM, cold agglutinin titer and thermal amplitude) this treatment failed to induce a clinical remission. This failure may be the result of the ability of the cold agglutinin to fix complement to the red cell membrane at temperatures much higher than the thermal amplitude. A simple laboratory test to detect this dissociation between complement fixing ability and agglutination activity is described.