Macfarlane et al present a comprehensive and thorough review of the multiplicity of factors affecting therapeutic decision making by general practitioners for patients presenting with acute lower respiratory tract symptoms.1 They do, however, pass very briefly over the evidence base for the use of antibiotics in this common and important clinical situation, citing only one original study, one review, and one meta-analysis to justify the statement that “antibiotics have little impact on the duration of symptoms of acute bronchitis”. For such an important and fundamental cause of morbidity in primary care there is an extraordinary dearth of studies to inform evidence-based decision making; the published studies are small, variable in quality, and use various antibiotics, dosage regimes, and outcome measures. In the quoted meta-analysis by Fahey et al 2 of randomised controlled trials comparing antibiotics with placebo, only nine studies investigating a total of 700 randomised patients were found for analysis. Only six of these studies were suitable for the analysis of some of the key outcomes. The authors' conclusion that antibiotic treatment has no effect on the resolution of acute cough was subsequently criticised.3-5

Although the clinical improvements analysed in the antibiotic treated group failed to reach statistical significance, quite narrowly for some outcomes, the results did favour antibiotics for an effect on both resolution of cough and clinical improvement at re-examination, suggesting a trend favouring the use of antibiotics over placebo. The wide confidence limits and the small numbers point to the need for further data. The Cochrane meta-analysis of the same data6reached very different conclusions, commenting that “the review confirmed the impression of clinicians that antibiotics have some beneficial effects in acute bronchitis”. The benefits are probably small and confined to certain patient subgroups, but the quantification of benefit and the definition of the characteristics of responder groups need further studies to delineate.

All responsible clinicians must be in favour of appropriate use of antimicrobial drugs and efforts to “raise the trigger line” for the use of such agents are laudable. The assertion that the majority of British GPs and their European colleagues are ignoring a good evidence base when they prescribe antibiotics in this situation would, however, appear to be premature. Clarification of which patients with acute lower respiratory symptoms will benefit and by how much can only assist us in targeting and restricting the use of antimicrobials. Increasingly well informed patients and GPs attempting to practice evidence-based medicine need such information to make rational decisions on appropriate management options. There is a need for well designed prospective placebo controlled, randomised trials performed in real world primary care settings with adequate power to provide definitive answers.