In vitro effect of blood cell counts on multiple-electrode impedance aggregometry in dogs

Abstract

OBJECTIVE To assess the effect of decreased platelet and WBC counts on platelet aggregation as measured by a multiple-electrode impedance aggregometer in dogs. ANIMALS 24 healthy dogs. PROCEDURES From each dog, 9 mL of blood was collected into a 10-mL syringe that contained 1 mL of 4% sodium citrate solution to yield a 10-mL sample with a 1:9 citrate-to-blood ratio. Each sample was then divided into unmanipulated and manipulated aliquots with progressively depleted buffy-coat fractions such that 2 to 3 blood samples were evaluated per dog. The Hct for manipulated aliquots was adjusted with autologous plasma so that it was within 2% of the Hct for the unmanipulated aliquot for each dog. All samples were analyzed in duplicate with a multiple-electrode impedance aggregometer following the addition of ADP as a platelet agonist. The respective effects of platelet count, plateletcrit, Hct, and WBC count on platelet aggregation area under the curve (AUC), aggregation, and velocity were analyzed with linear mixed models. RESULTS WBC count was positively associated with platelet AUC, aggregation, and velocity; blood samples with leukopenia had a lower AUC, aggregation, and velocity than samples with WBC counts within the reference range. Platelet count, plateletcrit, and Hct did not have an independent effect on AUC, aggregation, or velocity. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that WBC count was positively associated with platelet aggregation when ADP was used to activate canine blood samples for impedance aggregometry. That finding may be clinically relevant and needs to be confirmed by in vivo studies.

The effect of adding lactic acid to canine whole blood on platelet aggregation as measured by impedance aggregometry

“…where a wider range of cell counts was evaluated, 3 AUC was significantly associated with the WBC count. Because all blood samples for this study were obtained from healthy dogs, no severe hematologic abnormalities were present.…”

“…The platelet count was an exception to this rule, but all platelet counts were >100 000/µL. Previous work indicates that platelet aggregation is not affected if the platelet count is above 50 000/µL 3 . Blood smears were prepared from the blood in EDTA prior to sample manipulation and evaluated by a single investigator (CAL).…”

“…As a result, this strategy could be useful for the evaluation of platelet aggregation in sick animals . Previous studies using the Multiplate analyzer have examined preanalytical factors such as the effects of anticoagulant choice, 2 cell counts (RBC, WBC, and platelet count) in a blood sample, 3 and agonist storage time before analysis 4 . An understanding of the potential impact that these variables might have on results is necessary when using this methodology to evaluate platelets from sick animals.…”

Effects of storage conditions on two platelet agonists for whole blood impedance platelet aggregometry in dogs

“…Whole blood impedance platelet aggregometry (Multiplate) is a specialized assay that can be used to assess platelet function in dogs . Over the past several years, veterinary studies in dogs have used this assay, and it is being used clinically with an increasing frequency . This method uses anticoagulated whole blood and platelet agonists that stimulate platelets to aggregate.…”

“…The area under the curve (AUC) is the standard measurement reported that describes platelet responses to different agonists . Arachidonic acid (AA) and adenosine diphosphate (ADP) are two agonists that are used frequently in veterinary medicine . To perform the assay, reagents are reconstituted according to the manufacturer's (Multiplate 5.0 Analyzer; Diapharma Group Inc., West Chester, OH, USA) recommendations and can be stored in aliquots at 2‐8°C for 24 hours or ≤−20°C for 4 weeks.…”