Systemic inflammation has been reported to be present in COPD, as shown by increased levels of circulating interleukin (IL)-1 beta, IL-6, tumour necrosis factor-alpha (TNF-α), high-sensitivity C-reactive protein (CRP) and total white blood cell count (Sethi et al., 2012; Barnes, 2013; Chhabra et al., 2015; Okamoto et al., 2015). Here, CRP is linked to chronic obstructive pulmonary disease.