title: Platelet activation in patients with peripheral vascular disease: reproducibility and comparability of platelet markers.
abstract: BACKGROUND
  Many markers of platelet activation have been described but their reproducibility and comparability in patient populations are poorly defined.
  
  
  OBJECTIVE
  We sought to compare markers of platelet and monocyte activation with platelet-monocyte aggregates, a proposed gold standard of in vivo platelet activation, and assess their reproducibility in patients with peripheral arterial disease: a population with substantial platelet activation, inflammation and risk of thrombotic events.
  
  
  METHODS
  Thirty patients with peripheral vascular disease attended on two occasions to permit within-day and between-day comparisons. In vivo platelet and monocyte activation were determined by flow-cytometric quantification of platelet-monocyte aggregation, platelet surface expression of P-selectin and CD40L, platelet-derived microparticles, and monocyte surface expression of CD40 and CD11b. Plasma concentrations of platelet-derived microparticles, soluble P-selectin and CD40L were measured by enzyme-linked immunosorbant assays.
  
  
  RESULTS
  Platelet-monocyte aggregation (36.7±7.86%), and platelet surface expression of P-selectin (5.8±1.65%) and CD40L (3.3±1.45%) demonstrated comparable within-day (mean difference±co-efficient of reproducibility; 0.9±15.4%, 0.21±1.65% and 0.2±2.8% respectively) and between-day reproducibility (2.0±12.4%, 0.10±2.25% and 0.9±6.4% respectively). Platelet-monocyte aggregates correlated well with other platelet (r=0.30-0.50, P<0.02) and monocyte (r=0.27-0.47, P<0.03) activation markers. Flow cytometric and assay quantified platelet-derived microparticles showed poorer reproducibility (co-efficient of reproducibility >40).
  
  
  CONCLUSIONS
  In patients with peripheral arterial disease, measurements of platelet-monocyte aggregates have good reproducibility and consistently reflect other markers of platelet and monocyte activation.
authors.affiliation: The University of Edinburgh, Centre for Cardiovascular Sciences, UK. anne.burdess@ed.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Burdess
authors.forename: A E
authors.initials: AE
authors.lastname: Michelsen
authors.forename: F
authors.initials: F
authors.lastname: Brosstad
authors.forename: K A A
authors.initials: KA
authors.lastname: Fox
authors.forename: D E
authors.initials: DE
authors.lastname: Newby
authors.forename: A F
authors.initials: AF
authors.lastname: Nimmo
mesh_terms: D015415:Biomarkers / Q000097:blood*; D039481:CD11b Antigen / Q000097:blood; D019013:CD40 Antigens / Q000097:blood; D023201:CD40 Ligand / Q000097:blood; D055252:Cell-Derived Microparticles / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D015588:Observer Variation; D019007:P-Selectin / Q000097:blood; D016491:Peripheral Vascular Diseases / Q000097:blood* / Q000175:diagnosis / Q000276:immunology; D015539:Platelet Activation; D010973:Platelet Adhesiveness; D010979:Platelet Function Tests; D011237:Predictive Value of Tests; D011379:Prognosis; D015203:Reproducibility of Results; D012606:Scotland
chemical_list: D015415:Biomarkers; D039481:CD11b Antigen; D019013:CD40 Antigens; C509295:ITGAM protein, human; D019007:P-Selectin; C546937:SELP protein, human; D023201:CD40 Ligand