[Pseudoleucopenia due to in vitro leukocyte agglutination polynuclear neutrophils: experience of a laboratory, review of the literature and future management].

Leukoagglutination is a rare EDTA-dependent phenomenon resulting in a spurious minoration of the leukocyte count performed using automated analyzers. We described seven cases. The leukocyte agglutination was detected by unstable WBC count, abnormal WBC histograms and presence of clusters of polymorphonuclears on the smear. PMN aggregates of 3 to 10 cells or bigger were observed. Discrepancies between the erroneous automated WBC count and the real count were moderate in most cases. Leukoagglutination was related to lymphoproliferative disorders, infections, alcoholic liver diseases, auto-immune diseases. Inflammatory context seemed to be requested. For few patients, the artefact occurred regardless of the type of anticoagulants (lithium heparin, buffered sodium citrate) and warming at 37 C did not always increase the WBC. Dilution in Unopette chambers was required. We confirmed that leukoagglutination of PMN was an in vitro artefact EDTA and/or temperature mediated.