Acute exacerbation of COPD: Factors associated with poor treatment outcome

Objectives: To determine the effect of age, severity of lung disease, severity and frequency of exacerbation, steroid use, choice of an antibiotic, and the presence of comorbidity on the outcome of treatment for an acute exacerbation of COPD. Design: A retrospective chart analysis over 24 months. Setting: A university Veterans Affairs medical center. Patients: Outpatients with COPD who were treated with an antibiotic over a period of 24 months for an acute exacerbation of COPD. Methods: Severity of an acute exacerbation of COPD was defined using the criteria of Anthonisen et al: increased dyspnea, increased sputum volume, and increased sputum purulence. Severity of lung disease was stratified based on FEV₁ percent predicted using American Thoracic Society guidelines (stage I, FEV₁ ≥ 50%; stage II, FEV₁ 35 to 49%; stage III, FEV₁ < 35%). Treatment outcome was judged successful when the patient had no return visit in 4 weeks for a respiratory problem. Failure was defined as a return visit for persistent respiratory symptoms that required a change of an antibiotic in < 4 weeks. Results: One-hundred seven patients with COPD (mean age ± SD, 66.9 ± 9.5 years) experienced 232 exacerbations over 24 months. First-line antibiotics (trimethoprim- sulfamethoxazole, ampicillin/amoxicillin, and erythromycin) were used to treat 78% of all exacerbations. Treatment failure was noted in 12.1% of first exacerbations and 14.7% of all exacerbations, with more than half the failures requiring hospitalization. Host factors that were independently associated with treatment failure included the following: FEV₁ < 35% (46.4% vs 22.4%; p = 0.047), use of home oxygen (60.7% vs 15.6%; p < 0.0001), frequency of exacerbation (3.8 ± 2.0 vs 1.6 ± 0.91; p < 0.001), history of previous pneumonia (64.3% vs 35.1 p < 0.007), history of sinusitis (28.6% vs 8.8%; p < 0.009) and use of maintenance steroids (32.1% vs 15.2% p = 0.052). Using stepwise logistic regression analysis to identify the top independent variables, the use of home oxygen (p = 0.0002) and frequency of exacerbation (p < 0.0001) correctly classified failures in 83.3% of the patients. Surprisingly, age, the choice of an antibiotic, and the presence of any one or more comorbidity did not affect the treatment outcome. Conclusion: The results of our study suggest that patient host factors and not antibiotic choice may determine treatment outcome. Prospective studies in appropriately stratified patients are needed to validate these findings.