[Studies on EDTA-dependent pseudoneutropenia].

The phenomenon of EDTA-dependent pseudoleukocytopenia was observed in seven patients during the period from September 1989 to March 1990. The pseudoleukocytopenia was found to have come from aggregation of neutrophils. The aggregations were composed of neutrophils only, and did not include other granulocytes, monocytes and lymphocytes. The aggregations showed their maximum in size from 30 to 180 minutes after venipuncture at room temperature. The aggregated neutrophils were again dispersed by incubating at 37 degrees C for 30 minutes. The degree of aggregation was found to be dependent on the concentration of EDTA. Neutrophil aggregation was not recognized in the blood films when sodium citrate or heparin was used as an anticoagulant. The results of mercaptoethanol agglutination test and immunocytochemical staining suggest that IgM antibody may play an important role in the formation of neutrophil aggregation. Four of the seven patients had suffered from hepatic disorder. However, the mechanism of EDTA-dependent neutrophil aggregation remains uncertain.