PLATELET THROMBUS FORMATION IN CHRONIC HAEMODIALYSIS PATIENTS MEASURED BY THE TOTAL THROMBUS-FORMATION ANALYSIS SYSTEM

Abstract BACKGROUND AND AIMS Patients with end-stage renal disease (ESRD) receiving haemodialysis (HD) often experience bleeding. However, mechanisms behind this bleeding tendency are incompletely understood but may involve platelet dysfunction. We therefore studied platelet-dependent thrombus formation in flowing whole blood inside a microchip coated with collagen, and its association with circulating von Willebrand factor (VWF). METHOD Blood samples were obtained in 22 patients before and after HD. The area under the 10 min flow pressure curve in a microchip (AUC10) reflecting total platelet thrombogenicity was measured, using the Total Thrombus-formation Analysis System (T-TAS01). AUC10 < 260 indicates platelet dysfunction. VWF-antigen and measures of VWF-activity, i.e. VWF-RCo, VWF-CBA and latex-particle based VWF activity were also assayed. RESULTS VWF levels were moderately elevated and increased further after HD (P < 0.01 or lower). In contrast, AUC10 before and after HD was < 260 in 17/22 patients and < 130 in 15/22 patients, with no statistically significant difference in pre- versus post-HD measurements (median AUC10 in all patients 10.2 versus 20.3, respectively), altogether indicating reduced platelet thrombogenicity, but with some variability (5/22 patients with normal platelet responsiveness). AUC10 before and after HD correlated fairly well (r = 0.77, P < 0.001), and all VWF-related parameters (before versus after HD) were also correlated (r = 0.74 or higher; P < 0.0001). In contrast, no significant correlations were found between absolute values of AUC10 and any VWF-related parameters or between changes in values (i.e delta-values for differences between pre versus post HD). CONCLUSION Most ESRD-patients display moderate to severe platelet dysfunction as assessed by shear-induced collagen-dependent platelet thrombus formation with T-TAS01.Platelet thrombus formation under high shear, as measured by the collagen-coated PL-chip, is not importantly influenced by a moderate HD-induced increase in VWF. T-TAS01 should be further evaluated as a tool in the assessment of bleeding risk in patients on HD.