Background: Anthonisen criteria are widely used to guide the use of antibiotics in exacerbations of COPD. We evaluated the best predictors of outcomes in exacerbations of mild to moderate COPD not treated with antibiotics.
Methods: We used data from 152 patients of the placebo arm of a randomized trial of amoxicillin/clavulanate for exacerbations of mild to moderate COPD. Clinical response in relation to Anthonisen criteria and point-of-care serum C-reactive protein (CRP) tests (cutoff, 40 mg/L) was assessed with multivariate logistic regression analysis.
Results: Clinical failure without antibiotics was 19.9% compared with 9.5% with amoxicillin/clavulanate (P = .022). The only factors significantly associated with an increased risk of failure without antibiotics were the increase in sputum purulence (OR, 6.1; 95% CI, 1.5-25.0; P = .005) and a CRP concentration ≥ 40 mg/L (OR, 13.4; 95% CI, 4.6-38.8; P < .001). When both factors were present, the probability of failure without antibiotics was 63.7%. The Anthonisen criteria showed an area under the curve of 0.708 (95% CI, 0.616-0.801) for predicting clinical outcome. With the addition of CRP level, the area under the curve rose significantly to 0.842 (95% CI, 0.76-0.924; P < .001).
Conclusions: Among the Anthonisen criteria, only an increase in sputum purulence is a significant predictor of failure without antibiotics. The use of a point-of-care CRP test significantly increases the predictive accuracy of failure. Both of these easy-to-obtain factors may help clinicians to identify patients with exacerbated mild to moderate COPD who can be safely treated without antibiotics in an ambulatory setting.
Trial registry: ClinicalTrials.gov; No.: NCT00495586; URL: www.clinicaltrials.gov.