AJVR, Vol 66, No. 2, February 2005 325 P latelet activation in vivo may play an important role in the pathogenesis of a variety of conditions in dogs. Platelet aggregometry has been used to detect hyperaggregable platelets in dogs with multicentric lymphosarcoma, other malignancies, nephrotic syn- drome, and heartworm disease. 1–4 Hypoaggregable platelets have been detected in dogs with liver disease and experimentally induced pancreatitis. 5,6 No changes in platelet aggregation were detected in dogs with ure- mia. 7 Flow cytometry has been used to detect activation- dependent markers on circulating platelets. 8–12 Activation markers detected on the surface of canine platelets include P-selectin and fibrinogen bound to glycoprotein IIb-IIIa. 11–13 P-selectin is a component of the α-granule membrane and is expressed on the platelet surface after α-granules are secreted. 9,14 Two anti-canine P-selectin antibodies and 2 antibodies that cross-react with canine platelet P-selectin have been described. 11,15,16 We have described a flow-cytometric technique for detection of activated platelets in healthy dogs. 8 Activated platelets were detected via incubation of platelets with a mouse anti-canine P-selectin anti- body followed by incubation with a fluorescein- labeled, goat anti-mouse IgG antibody. The median fluorescence intensity (MFI) of the platelet popula- tion and the percentage of platelets with increased fluorescence intensity increased when platelets were activated via addition of phorbol myristate acetate (PMA). Recently developed techniques for automated detection of activated platelets include determina- tions of mean platelet component concentration (MPC) and mean platelet component distribution width (MPCDW). 17,18 The technique for determin- ing MPC measures the refractive index of platelets; refractive index is linearly related to platelet densi- ty. When activated platelets degranulate, platelet density decreases and therefore the MPC decreases. The MPCDW is an indicator of the variation in platelet density; therefore, if both nondegranulated and degranulated platelets are present in the circu- lation, the MPCDW is high. Mean platelet volume (MPV) is a measure of platelet size, and platelet distribution width (PDW) is an indicator of the variation in platelet size. The advantage of use of these variables is that they can be routinely deter- mined by use of an automated hematology analyz- er a ; however, the usefulness of these variables for detection of activated platelets in dogs has not been extensively evaluated. The purpose of the study reported here was to evaluate platelet surface-associated P-selectin, MPC, MPCDW, MPV, and PDW for detection of activated platelets in dogs with septic and nonseptic inflamma- tory disease. Materials and Methods Blood samples—Blood samples submitted to the clini- cal laboratory at the University of Minnesota Veterinary Received March 22, 2004. Accepted May 3, 2004. From the Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108. Dr. Moritz’s present address is Clinic for Internal Medicine and Forensic Affairs, Faculty of Veterinary Medicine, Justus-Liebig University, Giessen, Germany. Address correspondence to Dr. Weiss. Evaluation of flow cytometric and automated methods for detection of activated platelets in dogs with inflammatory disease Andreas Moritz, Dr med Vet PD; Bruce K. Walcheck, PhD; Douglas J. Weiss, DVM, PhD Objective—To evaluate platelet surface-associated P-selectin, mean platelet component concentration (MPC), mean platelet component distribution width (MPCDW), mean platelet volume (MPV), and platelet distribution width (PDW) for detection of activated platelets in dogs with septic and nonseptic inflamma- tory disease. Animals—20 healthy dogs and 20 dogs with septic and nonseptic inflammatory disease. Procedures—Platelet surface-associated P-selectin (expressed as the median fluorescence intensity [MFI] of the platelet population), MPC, MPCDW, MPV, and PDW were determined in 20 healthy adult dogs, and reference ranges were calculated. These parameters were also determined in 11 dogs with nonseptic and 9 dogs with septic inflammatory dis- ease and evaluated to determine which parameters were useful for detection of activated platelets. Results—12 dogs with inflammatory disease had P- selectin greater than the upper limit of the reference range, whereas 16 dogs with inflammatory disease had MPC lower than the lower limit of the reference range. All dogs in which P-selectin was greater than the upper limit of the reference range had MPC lower than the lower limit of the reference range. The corre- lation coefficient for P-selectin and MPC was 0.62. Differences in the MPCDW, MPV, and PDW in most dogs with inflammatory disease (compared with healthy dogs) were found; however, the correlation coefficients for P-selectin and MPCDW, MPV, and PDW were low. Conclusions and Clinical Relevance—Platelet sur- face-associated P-selectin and MPC appeared to be useful to detect activated platelets in most dogs with septic and nonseptic inflammatory disease. (Am J Vet Res 2005;66:325–329) Unauthenticated | Downloaded 11/22/23 07:05 PM UTC