Study objectives: To investigate the possible relationship between functional respiratory impairment measured by FEV1 and isolation of diverse pathogens in the sputum of patients with exacerbations of COPD.
Design: Multicenter, cross-sectional, epidemiologic study.
Setting: Pneumology units in six secondary or tertiary hospitals in Spain.
Patients: Ninety-one patients with acute exacerbation of COPD were included.
Interventions: A quantitative sputum culture was performed, and bacterial growth was considered significant only when the germ was isolated at concentrations > 10(6) cfu (> 10(5) for Streptococcus pneumoniae) in samples with < 10 epithelial cells and > 25 leukocytes per low magnification field (x 100).
Results: Germs isolated were the following: Haemophilus influenzae (20 cases; 22%), Pseudomonas aeruginosa (14 cases; 15%), S. pneumoniae (9 cases; 10%), Moraxella catarrhalis (8 cases; 9%), other gram-negative bacteria (7 cases; 7%), and non-potentially pathogenic microorganisms (non-PPMs; 33 cases; 36%). P. aeruginosa and H. influenzae were isolated more frequently among the patients with FEV1 < 50% than among those with FEV1 > 50% (p < 0.05). All patients with P. aeruginosa in sputum had FEV1 < 1,700 mL. FEV1 < 50% was associated with a very high risk of P. aeruginosa or H. influenzae isolation: the odds ratios (ORs) are 6.62 (95% confidence interval [CI], 1.2 to 123.6) and 6.85 (95% CI, 1.6 to 52.6), respectively. Furthermore, active tobacco smoking was associated with a high risk of H. influenzae isolation (OR, 8.1; 95% CI, 1.9 to 43.0).
Conclusions: Patients with the greatest degree of functional impairment, as measured by their FEV1, presented a higher probability of having an isolation of P. aeruginosa or H. influenzae in significant concentrations in sputum during an exacerbation. The diagnostic yield of sputum in patients with an FEV1 > 50% was low, with a predominance of non-PPMs. Low FEV1 and active tobacco smoking are data that should be considered when establishing an empiric antibiotic treatment for exacerbated COPD.