A comparison of platelet parameters in EDTA‐ and citrate‐anticoagulated blood in dogs

Abstract

Platelets aggregate, likely from activation, when blood from dogs with neoplasia is anticoagulated with citrate for hematology testing, resulting in lower platelet counts. Citrate also yields inaccurate results for MPV and MPC, likely because of inadequate sphering of platelets. Thus, we recommend that citrate not be used as an anticoagulant when accurate platelet counts are desired in dogs.

Effect of Anticoagulant and Storage Conditions on Platelet Size and Clumping in Healthy Dogs

“…9,23,29 Despite the fact that the overall frequency of platelet clumping in the present study may have been affected by a relatively low threshold for abnormality (at least 3 aggregates, each consisting of $3 platelets), clumping was significantly more frequent in citrate-compared to EDTA-anticoagulated blood and was more pronounced at lower temperatures. As is the case with cats, the prolonged storage of blood (up to 24 hr postsampling) does not appear to substantially accentuate this phenomenon in dogs.…”

“…6,7,28,31 In a 1986 study, 6 the maximum MPV was observed in EDTA-anticoagulated canine blood stored at 4uC, while minimum MPV alteration was observed in citrate-anticoagulated blood stored at 37uC. Interestingly, in a study published in 1989, 34 no EDTA-or storage temperature-mediated impact was demonstrated on the MPV of healthy dogs determined over a period of 30 hr postsampling in an impedance analyzer, while a 2007 study 29 demonstrated a significant increase of MPV in citrate-anticoagulated compared to EDTA-anticoagulated canine blood processed in an optical analyzer within an hour of collection. This discrepancy may be partially explained by the different study design (instrumentation, different blood sampling timing, number of dogs, consideration of macroplatelet percentages instead of MPV, concentration of EDTA, and different degrees of platelet activation or aggregation).…”

“…Despite this shortcoming, the microscopic reviewing of a blood smear still remains the most reliable method for detecting aggregates, thus validating the automated platelet enumeration, although QBC analyzer and some state-of-the-art optical analyzers may flag their presence in the blood. 9 In a recent study, the sensitivity and specificity of this platelet parameter (automated platelet clump count) generated by an optical analyzer appeared to be less than satisfactory, 29 as has been the case with the QBC analyzer. 9,23 In conclusion, the present study provides baseline data on the macroplatelet percentages in the blood of healthy dogs in a variety of preanalytical conditions.…”

“…7,32 Regardless, platelet clumping appears to be unavoidable (although with a different probability to occur) in a large proportion of canine blood samples using either citrate or EDTA, and future studies may be warranted to investigate if measures such as the collection of blood into anticoagulants containing platelet activation inhibitors or the vortex mixing of blood could minimize aggregation, as has been preliminarily documented in cats. 14,29,33 In addition, further studies should try to clarify if there are species differences in the clumping-inducing effect of citrate or EDTA. Although platelet clumping usually results from activation of platelets during blood collection and handling, the tendency for a more pronounced platelet clumping at 4uC versus 25uC in the present study raises the possibility of an anticoagulantdependent, cold agglutinin-mediated platelet agglutination, which has been frequently documented in people and rarely in horses but is apparently rare or underestimated in dogs, or of a nonspecific cold activation of normal platelets.…”

“…5,9,28 Historically, the use of citrate anticoagulant was associated with a reduced possibility of the formation of platelet clumps in canine blood 7,32 ; however, in a recent study, platelet aggregates were significantly more frequently visualized in stained blood smears prepared from citrate-anticoagulated blood as compared to ethylenediamine tetraacetic acid (EDTA)-anticoagulated blood. 29 The potential effect of temperature and blood storage time on the development of platelet clumping in the healthy dog is largely elusive, although cooling and storage of blood may reportedly accentuate the formation of aggregates. 7,12 The objective of the present study was to assess the effect of anticoagulant (EDTA vs. citrate), blood storage temperature (25uC vs. 4uC), and time (up to 24 hr postsampling) on the percentage of macroplatelets and the frequency of platelet aggregates, as observed by light microscopy, in blood smears from healthy nonthrombocytopenic dogs.…”