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Bird, in Small Animal Pediatrics, 2011 Platelet CountsĬommonly the number of platelets and mean platelet volume (MPV) are obtained when performing an automated hematological evaluation of EDTA anticoagulated blood. 490 Dogs with phosphofructokinase deficiency of erythrocytes and skeletal muscle have mildly increased MPVs with normal platelet counts. MPVs have been reported to be slightly higher in hyperthyroid cats and slightly lower in hypothyroid dogs than in euthyroid animals. 143 In fact, most dogs with an increased reticulated platelet count do not have an increased MPV. 143,280,385 Consequently a normal MPV does not rule out enhanced thrombopoiesis, especially in primary IMT in dogs. 164Īlthough the MPV is expected to be increased in response to thrombocytopenia, normal or even decreased MPVs have been associated with dogs and humans with immune-mediated thrombocytopenia (IMT), presumably because of the presence of platelet fragments (as opposed to the formation of small platelets). 127 A macrothrombocytopenia has also been reported in a pug dog with the May-Hegglin anomaly (see Fig.

54,147 Cavalier King Charles spaniel dogs with inherited macrothrombocytopenia have higher MPV values because of the occurrence of a population of macrothrombocytes. 366,548 However, the MPV can also be high in animals with myeloid neoplasms and, in cats, with feline leukemia virus (FeLV)-induced thrombocytopenia. The MPV has been reported to be increased in some dogs with nonimmune-mediated regenerative thrombocytopenia 143 as well as in inflammatory conditions that result in enhanced platelet utilization/destruction. 112,311 Interestingly, the MPV increased in mice within 8 hours after the production of thrombocytopenia, but 40 hours were required before increased megakaryocyte ploidy was observed. 424,551Ī high MPV value suggests the presence of increased thrombopoiesis. 179 These differences may be explained by the variable effects of anticoagulants on platelet activation and shape and by the various ways in which automated analyzers size platelets.

179,217 Discrepancies in the effect of temperature on MPV during storage have also been reported. 485 No change in MPV was found in EDTA-anticoagulated dog blood stored for a day in one study, 520 but increases in MPV have been reported with storage of EDTA-anticoagulated dog blood in other studies. The MPV was reported to be higher when dog blood was collected with EDTA versus citrate as the anticoagulant in an early study, 217 but the MPV was reported to be lower when dog blood was collected with EDTA versus citrate as the anticoagulant in a more recent study. Results from studies on the effects of anticoagulants and storage conditions on MPV are contradictory. 48 These values would be somewhat different if EDTA were used as the anticoagulant or if a different analyzer were used for the assays. 551 Of domestic animal species, cats had the highest MPVs (mean 11 fL), followed by dogs (mean 7.2 fL), horses (mean 5.0 fL), cattle (mean 4.8 fL), and goats (mean 4.2 fL) when blood was collected with sodium citrate and assayed using the same automated analyzer (Series 810, Baker Instruments Corp., Allentown, PA). Cell counters that count and size platelets using laser flow cytometry may be able to accurately measure the MPV in whole blood of cats, but platelet aggregates often form during blood collection in cats, resulting in spuriously high MPV values. 424 Impedance cell counters can accurately determine the MPV in whole blood from dogs and horses but not in whole blood from cats. MPV determinations vary considerably with the instrument and anticoagulant used for the assay. 34,35 An inverse correlation between platelet counts and MPVs has also been reported in cats and dogs but not in horses, cattle, or goats. Within the normal ranges of platelet counts and MPVs, there is an inverse correlation between platelet count and MPV and a direct correlation between MPV and megakaryocyte ploidy (i.e., larger megakaryocytes) in healthy humans. The mean platelet volume (MPV) is the average volume of a single platelet recorded in femtoliters (fL).

Harvey DVM, PhD, DACVP, in Veterinary Hematology, 2012 Mean Platelet Volume