title: Determination of inflammatory biomarkers in patients with COPD: a comparison of different assays.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is an inflammatory pulmonary disorder with systemic inflammatory manifestations that are mediated by circulating acute-phase reactants. This study compared an enzyme-linked immunosorbent assay (ELISA) to a nephelometric technique for the measurement of serum C-reactive protein (CRP) and serum amyloid A (SAA) and investigated how the choice of assay influenced the estimation of inflammation in patients with stable COPD.
  
  
  METHODS
  CRP and SAA concentrations measured by ELISA and nephelometry in 88 patients with COPD and 45 control subjects were used to evaluate the performance of these methods in a clinical setting.
  
  
  RESULTS
  With both assays, the concentrations of CRP and SAA were higher in COPD patients than in controls after adjustment for age and sex. There was a moderate correlation between the values measured by ELISA and those measured by nephelometry (logCRP: r = 0.55, p < 0.001; logSAA: r = 0.40, p < 0.001). However, the concentrations of biomarkers determined by nephelometry were significantly higher than those obtained with ELISA for CRP (mean difference = 2.7 (9.4) mg/L) and SAA (mean difference = 0.31 (14.3) mg/L).
  
  
  CONCLUSIONS
  Although the serum CRP and SAA concentrations measured by ELISA and nephelometry correlated well in COPD patients, the ELISA values tended to be lower for CRP and SAA when compared with nephelometric measurements. International standardization of commercial kits is required before the predictive validity of inflammatory markers for patients with COPD can be effectively assessed in clinical practice.
authors.affiliation: Unidad Médico-Quirúrgica de Enfermedades Respiratorias, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío, Sevilla, Spain. lcampos@separ.es
authors.forename: José L
authors.initials: JL
authors.lastname: López-Campos
authors.forename: Elena
authors.initials: E
authors.lastname: Arellano
authors.forename: Carmen
authors.initials: C
authors.lastname: Calero
authors.forename: Ana
authors.initials: A
authors.lastname: Delgado
authors.forename: Eduardo
authors.initials: E
authors.lastname: Márquez
authors.forename: Pilar
authors.initials: P
authors.lastname: Cejudo
authors.forename: Francisco
authors.initials: F
authors.lastname: Ortega
authors.forename: Francisco
authors.initials: F
authors.lastname: Rodríguez-Panadero
authors.forename: Ana
authors.initials: A
authors.lastname: Montes-Worboys
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D002097:C-Reactive Protein / Q000032:analysis*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D045853:Exhalation / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000276:immunology* / Q000378:metabolism; D000685:Serum Amyloid A Protein / Q000032:analysis*; D013030:Spain
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; D000685:Serum Amyloid A Protein; D002097:C-Reactive Protein