Background: Systemic aspects of chronic obstructive pulmonary disease (COPD) include oxidative stress and altered circulating levels of inflammatory mediators and acute-phase proteins. C-reactive protein (CRP) reflects total systemic burden of inflammation in several disorders and has been shown to upregulate the production of proinflammatory cytokines. The aim of this study was to evaluate circulating CRP levels to determine the value of CRP as a biomarker of systemic inflammation and as an indicator of malnutrition or severity of COPD in stable COPD patients in comparison to the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6).
Methods: Thirty-five male patients with stable COPD and 30 age- and sex-matched subjects with normal pulmonary function were admitted to the study. Serum CRP levels were measured using a commercially available kit with the turbidimetric method. Serum TNF-alpha and IL-6 concentrations were measured with ELISA kits.
Results: Sixty percent of the patients had severe or very severe and 40% moderate COPD. Serum CRP was significantly higher in stable COPD patients than in control subjects (p<0.001), while TNF-alpha and IL-6 concentrations were not statistically different. Serum TNF-alpha was higher in severe or very severe COPD patients (p=0.046). When the COPD patients with a low BMI were compared to those with a normal-to-high BMI, there was a significant difference in CRP (p=0.034) and TNF-alpha (p=0.037).
Conclusion: The present study confirms that circulating CRP levels are higher in stable COPD patients and may thus be regarded as a valid biomarker of low-grade systemic inflammation. In addition, CRP is significantly higher in COPD patients with a low BMI and thus, together with TNF-alpha, may be considered an indicator of malnutrition in COPD patients.