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Open Access Research article

Determination of inflammatory biomarkers in patients with COPD: a comparison of different assays

José L López-Campos12*, Elena Arellano2, Carmen Calero12, Ana Delgado3, Eduardo Márquez1, Pilar Cejudo1, Francisco Ortega12, Francisco Rodríguez-Panadero12 and Ana Montes-Worboys12

Author Affiliations

1 Unidad Médico-Quirúrgica de Enfermedades Respiratorias, Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, Sevilla, Spain

2 CIBER de Enfermedades Respiratorias (CIBERES), Sevilla, Spain

3 Departamento de Bioquímica, Hospital Universitario Virgen del Rocío, Sevilla, Spain

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BMC Medical Research Methodology 2012, 12:40  doi:10.1186/1471-2288-12-40

Published: 31 March 2012

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).

Conclusion

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.