[Automated hematology analysers and spurious counts. Part 1. Platelets]

Hematology analysers provide now quick, accurate, and reproducible cell blood counts. However, depending on detection methods, spurious counts may occur. If undetected, such spurious counts may lead to inappropriate medical care and to unneeded explorations. Focusing first on platelet counts, situations leading to spurious decrease include several preanalytical considerations, the major one corresponding to EDTA-induced platelet aggregation and to platelet satellitism around polymorphs. In other instances, related to the presence of small particles mimicking platelets, including fragmented red blood cells, lipids, cryoglobulins, fibrin strands, or cytoplasmic fragments of leukocytes, spurious elevation of platelet count may occur. According to the analyser and to the methods used for the determination of the cell blood count, flags or messages related to these spurious changes differ. For each spurious change, the authors describe the mechanism leading to the anomaly, the way the analysers generate flags, and what should be done to provide accurate results.