Cytoplasmic Fragmentation Associated with Lymphoid Leukemia in Ruminants: Interference with Electronic Determination of Platelet Concentration
M. Glade Weiser, Gary L. Cockerell, J. A. Smith, Wayne A. Jensen · Veterinary Pathology · 1989
Leukocyte cytoplasmic fragmentation is associated with human leukemia, usually with leukocyte concentrations in excess of 1 O0,000/J.1.2.4,6 Increased attention has been drawn to leukocyte cytoplasmic fragments with the common use of automated hematology analyzers, and the recognition that such fragments interfere with the whole blood platelet counting capability of these instruments and by microscopy on hemocytometers. 1.2.4.6 This report documents interference of prominent leukemia-associated leukocyte fragmentation with automated electronic determination of platelet concentration in a cow and a sheep. This observation is important in veterinary hematology because it represents a morphologic feature of leukemia in animals and may result in errant enumeration of platelets by a variety of techniques. The S-Plus series of automated blood cell counters determines blood platelet concentration by mathematical analysis of both particle size distribution and concentration within a size range window encompassing approximately the lower third ofthe potential platelet volume range. This size window is about 1.3-1 3 fl on most automated cell counters modified for use in veterinary hematology. The instrument calculates platelet concentration after fitting a log normal curve to raw data in the size window (Fig. IA). In order for the curve fitting routine to function it must detect one mode between two minimum points within the size window. Furthermore, the mode must be between 2 fl and 10 fl on the modified system. If any of these criteria are not met, curve fitting is not done, an incomplete computation occurs, and platelet concentration is not printed. A cow and a sheep were evaluated hematologically by examination of Wright-Giemsa-stained blood films and an automated hemogram. Hemograms were done on an automated multi-channel analyzer modified for use in veterinary hematology by increasing the erythrocyte-platelet aperture bath current to 225 V (Coulter Counter Model S-Plus IV with histogram capability, Coulter Electronics Inc., Hialeah, FL). Platelet adequacy was estimated by blood film examination: no attempt was made to enumerate platelets by hemocytometer. The sheep was a 13-month-old black face ewe, which had been inoculated experimentally at 3 weeks of age with bovine leukemia virus (BLV) and was BLV-seropositive. Hematologic evaluation revealed severe nonregenerative anemia (hematocrit = 0.13) and extreme leukocytosis. The blood was diluted 1 : 10 to determine the leukocyte concentration. The total leukocyte concentration was 699,00O/pl, with 100°/o lymphoblasts. The sheep was killed for necropsy and was found to have multicentric lymphosarcoma consistent with that described following experimental infection with BLV.5 A 7-year-old Holstein cow suspected to have a displaced abomasum was brought to the Colorado State University. Masses were present in regions of the thoracic inlet, supra177