A case of EDTA-induced pseudo-neutropenia

The automated hematology analyzer, ADVIA2120i (SIEMENS), sorts blood cells by flow cytometry and counts the white blood cell (WBC) number separately in the Perox channel and Baso channel. One patient showed a large difference in the WBC numbers between the Perox channel and Baso channel. The scattergram of this patient indicated deviate clumps, suggesting agglutination of neutrophils. In fact, we confirmed massive agglutination of neutrophils with a microscopy. This agglutination of neutrophils may cause the apparently lower WBC count on the Perox channel. The agglutination was not induced by anticoagulants other than ethylene diamine terra acetic acid (EDTA). Therefore, we conclude that this is a case of EDTA-induced pseudo-neutropenia. To further confirm, we added the patient's serum to a healthy volunteer blood containing K2-EDTA, trisodium citrate, or heparin. The agglutination of neutrophils was observed only in K2-EDTA-containing blood. The agglutination-causing factor in the patient serum remains to be identified.