The C-Reactive Protein Testing to Guide Antibiotic Prescribing for COPD Exacerbations (PACE) study involved 653 patients with moderate exacerbations,70 while the CRP-guided antibiotic treatment in acute exacerbations of COPD in hospital admissions (CATCH) trial randomised 101 patients with severe exacerbations.71 In both trials, use of CRP led to a modest decrease in antibiotics use (20.4% and 15.5% absolute decrease), without any adverse impact on the clinical outcomes. This evidence concerns the gene CRP and chronic obstructive pulmonary disease.