CRP and bronchitis: Increasing C-reactive protein (CRP) levels by tenfold (OR = 5.14; 95% CI, 3.34–8.12; p < 0.001) or suspected chest infection on a radiograph (OR = 5.81; 95% CI, 3.23–10.89; p < 0.001) increased the OR of antibiotic treatment by fivefold.