Platelet parameters from an automated hematology analyzer in dogs with inflammatory clinical diseases
Introduction
Platelet activation during systemic inflammatory conditions may contribute to the development of macro- or micro-thrombi, which can result in significant morbidity and mortality in hospitalized patients (Christopherson et al, 2012, Wiinberg et al, 2012, Kidd, Mackman, 2013). There is therefore interest in monitoring the platelet activation status in hospitalized patients. Early detection of patients at risk of thromboembolism might allow initiation of thromboprophylaxis and monitoring of the response of platelets to these therapies. Flow cytometric detection of activation markers and platelet microparticles has been described in dogs, but has not been extensively studied in a clinical setting (Moritz et al., 2003).
The automated ADVIA 120 Hematology System (Bayer Corporation) uses two-dimensional (2D) laser technology to identify and characterize the size and complexity of cells in EDTA-anticoagulated whole blood. The two light scatter signals generated by each platelet are converted into multiple parameters that represent the number, size, and complexity of platelets in humans (Table 1) (Macey et al, 1999, Giacomini et al, 2001). Similarly, the laser technology also allows canine platelets to be distinguished from erythrocytes and generates an accurate platelet count (Welles et al., 2009). The mean platelet volume (MPV) is a measure of the mean platelet size, while the platelet distribution width (PDW) indicates the variation in platelet size and the plateletcrit is the product of the platelet count and MPV, representing the percent of a deciliter of blood occupied by platelets (similar to hematocrit for erythrocytes). The mean platelet component (MPC) is a measure of the refractive index of platelets and is related linearly to platelet density (Barer et al., 1953), generating an indirect index of the platelet activation status (Thompson et al, 1982, van Oost et al, 1983, Corash, 1990, Zelmanovic, Hetherington, 1998). Once activated, platelets release procoagulant substances from alpha and dense granules, reducing platelet density, and therefore decreasing the MPC (Chapman et al., 2003).
Reference values for canine platelet parameters using the ADVIA 120 analyzer have been established by Moritz et al. (2004). Since then, studies have evaluated the effect of storage (Furlanello et al, 2006, Prins et al, 2009), anticoagulants (Stokol and Erb, 2007), and hemolysis (Bauer et al., 2010) on ADVIA platelet parameters. Some studies have also evaluated canine platelet parameters in response to experimentally-induced and spontaneous inflammatory diseases (Moritz et al, 2005, Rafaj et al, 2005, Yilmaz et al, 2008, Flatland et al, 2011).
The purpose of this study was to evaluate platelet parameters in dogs with a large number of disease states that are generally associated with systemic inflammation, and to compare them with a control series of dogs presenting for elective orthopedic surgery. Our hypothesis was that the MPC would be lower in clinical conditions thought to cause platelet activation.
Section snippets
Study design
The medical records of dogs that presented to the University of Georgia Veterinary Teaching Hospital (UGA-VTH) between 1 January 2007 and 31 August 2009 were reviewed by two clinicians (JRS, KS). Canine coded diagnoses selected were primary immune-mediated hemolytic anemia (IMHA), primary immune-mediated thrombocytopenia (ITP), pituitary-dependent hyperadrenocorticism, intra-abdominal sepsis, pancreatitis, thrombi or thromboembolism (including diagnosis or strong suspicion of pulmonary
Results
A total of 228 dogs were included in the study, grouped by diagnosis into control dogs (n = 19), and those with hyperadrenocorticism (n = 47), hemangiosarcoma (n = 27), IMHA (n = 37), ITP (n = 32), pancreatitis (n = 32), sepsis (n = 25), and thrombotic disease (n = 9) (Table 2). The hemangiosarcoma animals were older than the control group (P < 0.001) (Table 2). Dogs with hyperadrenocorticism, IMHA and pancreatitis weighed less than the control dogs (P < 0.001) (Table 2). CBC analysis showed
Discussion
The results of this study did not support our hypothesis that a decreased MPC would be lower in canine patients with inflammatory disease. The MPC was lower in dogs with ITP compared with dogs with other diseases and the control dogs. The lower MPC in the ITP group may have represented the presence of circulating immature platelets with a decreased granularity compared with mature platelets. Alternatively, interactions with platelet-bound antibodies or the reticuloendothelial system may have
Conclusions
Based on the results of this study, the MPC is not consistently altered in certain canine diseases associated with systemic inflammation. Thus, it is not useful as a sole parameter to evaluate the risk of thromboembolism in hospitalized patients.
Conflict of interest statement
None of the authors of this paper has a financial or personal relationship with other people or organizations that could inappropriately influence or bias the content of the paper.
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