CRP and chronic obstructive pulmonary disease: This association could not be reproduced in patients with moderate to severe COPD [23], and even though the level of CRP is increased in patients with COPD compared with controls [24], it is an unspecific acute phase reactant and displays a wide variability in stable subjects with COPD over three months [25], which makes it less appropriate as a prognostic marker in this stratum of COPD.