title: Sandwich immunoassay for soluble glycoprotein VI in patients with symptomatic coronary artery disease.
abstract: BACKGROUND
  Platelet glycoprotein VI (pGPVI) expression is increased in acute coronary syndrome (ACS), reflecting platelet activation. There is no reliable method available to measure pGPVI. Our aim was to develop a bead-based sandwich immunoassay to measure soluble GPVI (sGPVI).
  
  
  METHODS
  Based on antibodies for sGPVI developed earlier, we established and validated a bead-based sandwich immunoassay in 2438 consecutive patients with stable angina pectoris (SAP; n = 1371), non-ST-elevation myocardial infarction (NSTEMI; n = 724), and ST-elevation MI (STEMI; n = 343). In a subgroup (n = 1011), we measured surface expression of pGPVI using flow cytometry.
  
  
  RESULTS
  The assay revealed a working range of 8-500 ng/L. Intra- and interassay imprecision was <7% and <14%, respectively. Patients with NSTEMI and STEMI showed significantly lower mean sGPVI concentrations than patients with SAP [mean (SD), 8.4 (3.6) μg/L and 8.6 (4.1) μg/L vs 9.8 (4.8) μg/L; P = 0.002], whereas subgroup analysis revealed significantly enhanced pGPVI in NSTEMI (n = 276) and STEMI (n = 80) patients compared with SAP (n = 655) [mean fluorescence intensity (SD), 21.2 (8.1) and 19.8 (6.8) vs 18.5 (7.7); P = 0.002 and P = 0.018]. pGPVI and sGPVI were inversely correlated (r = -0.076; P = 0.023). Area under the ROC curve was 0.716, 95% CI 0.681-0.751, for sGPVI, distinguishing patients with SAP from those with ACS, and was superior (P = 0.044) to the curve of subgroup analysis for pGPVI (0.624, 95% CI 0.586-0.662). sGPVI (P = 0.023) and pGPVI (P = 0.028) had better association with the development of ACS than troponin I (P = 0.055) in the very early stage of disease, based on logistic regression analysis.
  
  
  CONCLUSIONS
  This sandwich immunoassay reliably measures sGPVI and may help to identify patients with ACS earlier than other laboratory markers.
authors.affiliation: Medizinische Klinik, Klinik für Kardiologie und Kreislauferkrankungen, Eberhard Karls-Universität Tübingen, Germany. boris.bigalke@med.uni-tuebingen.de
authors.forename: Boris
authors.initials: B
authors.lastname: Bigalke
authors.forename: Oliver
authors.initials: O
authors.lastname: Pötz
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.forename: Tobias
authors.initials: T
authors.lastname: Geisler
authors.forename: Peter
authors.initials: P
authors.lastname: Seizer
authors.forename: Valentina O
authors.initials: VO
authors.lastname: Puntmann
authors.forename: Alkystis
authors.initials: A
authors.lastname: Phinikaridou
authors.forename: Amedeo
authors.initials: A
authors.lastname: Chiribiri
authors.forename: Eike
authors.initials: E
authors.lastname: Nagel
authors.forename: Rene M
authors.initials: RM
authors.lastname: Botnar
authors.forename: Thomas
authors.initials: T
authors.lastname: Joos
authors.forename: Meinrad
authors.initials: M
authors.lastname: Gawaz
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood / Q000175:diagnosis; D000368:Aged; D000787:Angina Pectoris / Q000097:blood / Q000175:diagnosis; D015415:Biomarkers / Q000097:blood; D003324:Coronary Artery Disease / Q000097:blood / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis; D010980:Platelet Membrane Glycoproteins / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012995:Solubility
chemical_list: D015415:Biomarkers; D010980:Platelet Membrane Glycoproteins; C098341:platelet membrane glycoprotein VI