title: Influence of sample type and storage conditions on soluble CD40 ligand assessment.
abstract: BACKGROUND
  Several studies have consistently shown that soluble CD40 ligand (sCD40L) concentrations are increased in patients with acute coronary syndromes and can serve as a biomarker for risk stratification. However, few data are available on preanalytic conditions that impact sCD40L values. Thus, the aim of our prospective study was to evaluate the impact of sampling techniques and storage conditions on sCD40L concentrations.
  
  
  METHODS
  We included a total of 30 patients with no, stable, or unstable coronary heart disease. Blood samples were collected in gel-filled tubes without additives, in EDTA-filled tubes, and in citrate-filled tubes and were kept at various storage conditions.
  
  
  RESULTS
  Median (interquartile range) sCD40L values at baseline were higher in serum samples [5.29 (3.89-6.33) microg/L] than in either EDTA plasma [0.78 (0.39-1.12) microg/L; P <0.001] or citrate plasma [0.37 (0.22-0.51) microg/L; P <0.001]. Serum values increased with delayed processing [7.94 (5.97-9.62) microg/L after 1.5 h (P <0.001) vs baseline; 10.55 (7.58-11.55) microg/L after 3 h (P <0.001) vs baseline]. However, after centrifugation, sCD40L values remained stable for all 3 sample types.
  
  
  CONCLUSIONS
  Plasma, but not serum, samples are appropriate for sCD40L measurements. In general, preanalytic conditions are critical in the assessment of sCD40L concentrations and thus should be carefully considered for future studies.
authors.affiliation: Kerckhoff Heart Center, Department of Cardiology, Bad Nauheim, Germany. M.Weber@kerckhoff-klinik.de
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Birgitt
authors.initials: B
authors.lastname: Rabenau
authors.forename: Michael
authors.initials: M
authors.lastname: Stanisch
authors.forename: Albrecht
authors.initials: A
authors.lastname: Elsaesser
authors.forename: Vesselin
authors.initials: V
authors.lastname: Mitrovic
authors.forename: Christopher
authors.initials: C
authors.lastname: Heeschen
authors.forename: Christian
authors.initials: C
authors.lastname: Hamm
mesh_terms: D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection; D023201:CD40 Ligand / Q000097:blood*; D003327:Coronary Disease / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010949:Plasma; D011446:Prospective Studies; D044967:Serum; D012995:Solubility
chemical_list: D015415:Biomarkers; D023201:CD40 Ligand