Background: Chronic obstructive pulmonary disease (COPD) is an inflammatory pulmonary disorder with systemic\ninflammatory manifestations that are mediated by circulating acute-phase reactants. This study compared an\nenzyme-linked immunosorbent assay (ELISA) to a nephelometric technique for the measurement of serum Creactive\nprotein (CRP) and serum amyloid A (SAA) and investigated how the choice of assay influenced the\nestimation of inflammation in patients with stable COPD.\nMethods: CRP and SAA concentrations measured by ELISA and nephelometry in 88 patients with COPD and 45\ncontrol subjects were used to evaluate the performance of these methods in a clinical setting.\nResults: With both assays, the concentrations of CRP and SAA were higher in COPD patients than in controls after\nadjustment for age and sex. There was a moderate correlation between the values measured by ELISA and those\nmeasured by nephelometry (logCRP: r = 0.55, p < 0.001; logSAA: r = 0.40, p < 0.001). However, the concentrations\nof biomarkers determined by nephelometry were significantly higher than those obtained with ELISA for CRP\n(mean difference = 2.7 (9.4) mg/L) and SAA (mean difference = 0.31 (14.3) mg/L).\nConclusion: Although the serum CRP and SAA concentrations measured by ELISA and nephelometry correlated\nwell in COPD patients, the ELISA values tended to be lower for CRP and SAA when compared with nephelometric\nmeasurements. International standardization of commercial kits is required before the predictive validity of\ninflammatory markers for patients with COPD can be effectively assessed in clinical practice.
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