antibodies in COPD. (A) IgG1 antibody levels specific to rhinovirus (VP1) are plotted for stable and exacerbation-prone COPD patients with the medians indicated. The lower limit of detection is highlighted with a dotted line. Significance was assessed by Mann–Whitney test with significant differences indicated. (B) The relationship between the number of hospitalisations and IgG1 antibody levels specific to rhinovirus (VP1) is shown with the regression line. The correlation was assessed using the Spearman rank test.