Spurious automated platelet count. Enumeration of yeast forms as platelets by the cell-DYN 4000.

We recently encountered a patient with thrombocytopenia secondary to multiple drug therapy, disseminated prostatic adenocarcinoma, and sepsis who had a sudden decrease in his platelet count as enumerated by the Cell-DYN 4000 hematology analyzer (Abbott Diagnostics, Santa Clara, CA). A manual platelet count performed thereafter was even lower. The etiology of the spurious platelet count was clarified when numerous yeast forms were observed on routine microscopy of the peripheral blood smear. Subsequently, these organisms were identified as Candida glabrata from a positive blood culture (BACTEC 9240, Becton Dickinson, Cockeysville, MD). To our knowledge, this is the first report of spurious enumeration of yeast forms as platelets in an automated hematology system. The principle underlying platelet enumeration by the Cell-DYN 4000 system and other hematology analyzers and the value of microscopy on peripheral smears with unexpected CBC count results are discussed. The timely reporting of accurate platelet counts is part of standard operating procedure in a hematology laboratory. The accuracy of platelet counts is of particular clinical relevance when thrombocytopenic patients near the transfusion threshold. The former “gold standard” of manual or hand platelet counting has a long turnaround time, is costly, and has questionable accuracy. Automated methods for platelet counting have been in existence since the 1950s when the impedance principle was introduced by Wallace Coulter. Despite substantial technical advances in hematology analyzers, a number of factors continue to interfere with automated platelet counts.