Bronchoscopic validation of the significance of sputum purulence in severe exacerbations of chronic obstructive pulmonary disease

Background: Antibiotics are commonly prescribed in exacerbations of chronic obstructive pulmonary disease (COPD). However, the role of bacteria in these exacerbations is controversial. Objective: To identify clinical predictors of bacterial infection as a cause of exacerbation, considering the protected specimen brush (PSB) as the gold standard. Methods: Clinical data, sputum and PSB samples were collected from 40 patients with COPD requiring hospitalisation due to severe exacerbations who had not received previous antibiotic treatment. Results: Quantitative cultures of PSB samples (n = 40) yielded 23 potential pathogenic microorganisms (PPMs) at concentrations of >= 10(2) colony-forming units/ml in 18 (45%) patients. Sputum samples were obtained from all 40 patients. Culture of good-quality sputum samples (n = 18) yielded 16 PPMs corresponding to 14 (35%) patients. The concordance between the PSB and sputum rate was high (kappa = 0.85, p < 0.002). The self-reporting patient observation of sputum purulence (odds ratio (OR) 27.20 (95% confidence interval (CI) 4.60 to 60.69), p = 0.001), the percentage predicted forced expiratory volume in 1 s (FEV1%) < 50 (OR 2.27 (95% CI 1.55 to 3.21), p = 0.014), > 4 exacerbations in the past year (OR 6.9 (95% CI 0.08 to 1.08), p = 0.028) and previous hospitalisations due to COPD (OR 4.13 (95% CI 1.02 to 16.07), p = 0.041) were associated with the presence of PPMs in the distal airways. The operative characteristics for predicting distal airway infection when patients presented with purulent exacerbation were as follows: sensitivity 89.5%, specificity 76.2%, positive predicted value 77.3% and negative predicted value 88.9%. Conclusions: The self-reporting presence of purulence in the sputum, as well as common previous exacerbations and hospitalisations due to COPD in patients with severe airflow obstruction (FEV1%,50) predict the presence of bacterial infection in the distal airways. The use of these clinical variables may help in selecting candidates to receive antibiotic treatment.