The study was designed to extend retrospectively the analysis of a previously reported study on chronic bronchitis patients with acute exacerbations treated with amoxicillin-clavulanic acid or matched placebo. We retrospectively re-clustered patients on the basis of severity of baseline lung function: Cluster 1 (104 patients) mean screening FEV(1)32.67+/-6.83 (SD); Cluster 2 (109 patients) mean screening FEV(1)54.12+/-5.56; Cluster 3 (122 patients) mean screening FEV(1)71.54+/-5.51. The success rate in the antibiotic group was significantly greater compared to the placebo group (P<0.001). When clinical improvement was analysed on the basis of patient re-clustering, 31.4% of Cluster 1 (severe COPD) patients treated with amoxicillin/clavulanate showed clinical improvement, whereas success was recorded in 58.8%. Conversely, 13.2% of Cluster 1 patients receiving placebo improved and 17% successfully recovered (P<0.001). Mild and moderate COPD patients (Clusters 2 and 3) were grouped together. In these two groups, 31.2% and 53.6% of patients receiving antibiotic treatment showed improvement or recovery, respectively, compared to 29.2% improvements and 30.2% successful recoveries among placebo-treated patients (P<0.001). In placebo-treated patients the improvement/success vs. failure rate was significantly different in Cluster 1 patients compared to Cluster 2+3 subjects (P<0.01, (2)test). The differences in final FEV(1)values in the treatment group and placebo group were significantly different (P<0.01) in favour of the active treatment group. Among more severe patients (Cluster 1), the comparison between screening and follow up FEV(1)values showed an improvement following antibiotic treatment and worsening after placebo (P<0.01). In Clusters 2 and 3 the difference between screening and follow up FEV(1)values was not significant for both treatment groups. Our patients with severe functional impairment and higher number of exacerbations per year are those who derive the greatest benefit from antibiotic treatment.
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