MO739EX VIVO THROMBOCYTE FUNCTION IN HEMODIALYSIS PATIENTS

Background and Aims Coagulation disorders with both risk for bleeding and thrombotic events are common in hemodialysis (HD) patients. Altered thrombocyte counts and function may account for that. Here, we sought to better characterize thrombocyte function in hemodialysis patients. Method Platelet function was investigated using the Multiplate analyzer (Roche) based on impedance aggregometry. Adenosine diphosphate (ADP) was used to induce platelet aggregation and area under the curve (AUC) was used as primary endpoint. Platelet counts and C-reactive protein (CRP) levels were measured. Hospitalization was the primary clinical outcome. Pearson regression was used to test for associations of thrombocyte function and the primary endpoint. Results In total 60 chronic HD patients undergoing dialysis 3 times per week, and 67 healthy controls were included. In general, HD patients presented with significantly lower thrombocyte numbers compared to healthy controls (Median: 221 vs. 245 G/l, p=0.029). Further, thrombocyte function as determined by AUC was significantly altered in HD patients versus healthy controls (Median: 455 vs. 677 AU*min, p<0.001; figure 1) with a significant correlation for platelet count and platelet function (r=0.42, p=0.001). Platelet function also correlated with the inflammatory state as seen by systemic CRP levels (r=0.28, p=0.033). Regarding the clinical outcome, platelet function correlated with hospitalization rates for infectious disease (r=0.27; p=0.040) and cardiovascular events (r=0.30; p=0.022). In case of hospitalization rates for infectious disease this correlation remained stable irrespective of adjustment for thrombocyte counts (r=0.27, p=0.036). Conclusion Lower platelet counts and altered function in HD patients was associated with risk of hospitalization and markers of inflammation in this cohort. The Multiplate analyzer appeared to be a valid and easily accessible method to assess thrombocyte function. Further studies are needed to determine whether assessment of thrombocyte function in clinical routine should be used to stratify risk in the vulnerable population of HD patients.

Rapid Cytoreduction by Plateletapheresis in the Treatment of Thrombocythemia

The objective of this chapter is to provide a systematic overview of current knowledge regarding therapeutic apheresis—primarily therapeutic plateletapheresis (TP)—and to summarize evidence-based practical approaches related to cytapheresis treatment of “hyperthrombocytosis” or “extreme thrombocytosis” (ETC). Our results of platelet (Plt) quantitative/qualitative analyses and evaluation of efficacy of apheresis systems/devices—on the basis of Plt removal and in vivo Plt depletion—will be presented. Our preclinical researches confirmed that in Plt concentrates, the initial ratio of discoid shapes was 70%, spherical 20%, and less valuable (dendritic/balloonized) shapes 10%—with morphological score of platelets (MSP = 300–400). After storage, the ratio of discoid and spherical shapes was decreased, while the less valuable ones progressively increased (MSP = 200). Electron microscopy has shown discoid shapes with typical ultrastructural properties. Spherical shapes with reduced electron density and peripheral location of granules/organelles were detected. Also, dendritic shapes with cytoskeletal “rearrangement,” membrane system integrity damages, and pseudopodia formations were documented. Our clinical study demonstrated that TP was useful in ETC treatment and should help prevention of “thrombo-hemorrhagic” events—until chemotherapy, antiplatelet drugs, and other medication take effect. During TP treatment, Plt count and morphology/ultrastructure were examined. Plt functions by multiplate analyzer were evaluated. We concluded that intensive TP was an effective, safe, and rapid cytoreductive treatment for ET.

Platelet Aggregation in Healthy Participants is Not Affected by Smoking, Drinking Coffee, Consuming a High-Fat Meal, or Performing Physical Exercise

Platelet aggregation can be measured using optical aggregation (light transmission aggregometry, LTA) as well as by impedance (Multiplate analyzer). The LTA (the gold standard method) can be influenced by many preanalytical variables. Several guidelines differ in recommendations for the duration patients should refrain from smoking, coffee, fatty meals, and physical exercise prior to blood collection for performing platelet function tests. In this pilot study, the influence of smoking, coffee, high-fat meal, or physical exercise on platelet aggregation was investigated to improve patient friendliness and laboratory logistics in platelet function diagnostics. Standardized blood collection was performed when participants were fasting and after each parameter (n=5 per group). As a control for diurnal fluctuations, participants (n=6) were fasting during both blood collections. Platelet aggregation was executed using standardized methods for LTA and Multiplate analyzer. Statistical analysis of the results using Wilcoxon signed-rank test did not show any significant differences in platelet aggregation in healthy participants under different preanalytical variables. Therefore, these variables are not expected to adversely affect testing, which can avoid canceling tests for those patients who inevitably did.

Which platelet function test best reflects the in vivo plasma concentrations of ticagrelor and its active metabolite?

SummaryAim of this study was assessment of the relationship between concentrations of ticagrelor and its active metabolite (AR-C124910XX) and results of selected platelet function tests. In a single-centre, cohort study, patients with myocardial infarction underwent blood sampling following a 180 mg ticagrelor loading dose intake (predose, 1, 2, 3, 4, 6, 12, 24 hours postdose) to perform pharmacokinetic and pharmacodynamic assessments. Platelet reactivity was evaluated using the VASP-assay, the VerifyNow device and the Multiplate analyzer. Analysis of 36 patients revealed high negative correlations between ticagrelor concentrations and platelet reactivity evaluated with all three platelet function tests (the VASP-assay: RS=-0.722; p<0.0001; the VerifyNow device: RS=-0.715; p<0.0001; the Multiplate analyzer: RS=-0.722; p<0.0001), with no significant differences between correlation coefficients. Similar results were found for AR-C124910XX. Platelet reactivity values assessed with all three methods generally correlated well with each other; however, a significantly higher correlation (p<0.02) was demonstrated between the VerifyNow and Multiplate tests (RS=0.707; p<0.0001) than in other assay combinations (the VASP-assay and the VerifyNow device: RS=0.595; p<0.0001; the VASP-assay and the Multiplate analyzer: RS=0.588; p<0.0001). With respect to the recognition of high platelet reactivity, we found higher measurement concordance between the VerifyNow and Multiplate tests compared with other assay combinations, while for low platelet reactivity, only results of the VerifyNow and Multiplate assay were related to each other. Platelet reactivity measurements performed with the VASP, VerifyNow and Multiplate tests show comparably strong negative correlations with ticagrelor and AR-C124910XX concentrations.Study registration: ClinicalTrials.gov identifier NCT02690454.