Family Practice Vol. 18, No. 3, 246-248
© Oxford University Press 2001
Infectious Diseases |
Re-evaluation of a randomized controlled trial of antibiotics for minor respiratory illness in general practice
Division of Primary Health Care, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR and
a Department of General Practice, University of Edinburgh, Levinson House, 20 West Richmond Street, Edinburgh EH8 9DX, UK.
Fahey T and Howie J. Re-evaluation of a randomized controlled trial of antibiotics for minor respiratory illness in general practice. Family Practice 2001; 18: 246–248.
Received 13 June 2000; Revised 3 October 2000; Accepted 8 January 2001.
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Abstract |
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Background. A systematic review examining the efficacy of antibiotics in acute respiratory illness concluded that antibiotics are of little benefit. However, that review was based on analysis of only six randomized controlled trials, one of which was excluded because its analysis included patients with multiple episodes of illness; treatment group, either antibiotic or placebo, might have confounded the likelihood of suffering a subsequent episode of illness.
Methods. This previously excluded randomized controlled trial of 301 patients with symptoms of minor respiratory illness was re-analysed to examine the efficacy of antibiotic versus placebo in terms of resolution of symptoms, most particularly cough.
Results. Antibiotic had no impact on the resolution of symptoms of cough at 1 and 2 weeks, respectively; adjusted odds ratio 1.2 [95% confidence interval (CI) 0.7–2.1] and 0.8 (95% CI 0.4–1.6). In those 220 (73%) individuals who suffered a cough, 48 (44%) and 19 (17%) of patients taking placebo were still coughing after 1 and 2 weeks, respectively.
Conclusion. It appears that an antibiotic is likely to have, at best, a marginal impact on resolution of symptoms for most patients with minor respiratory illness in the community.
Keywords. Antibiotics, cough, respiratory illness.
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Introduction |
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Acute respiratory illness is a common reason for seeking medical care. There remains a need for better information about the natural history of the condition and whether antibiotics are effective in reducing the symptoms of illness.1 A systematic review examining the efficacy of antibiotics concluded that antibiotics are of little benefit. However, that review was based on analysis of only six randomized controlled trials including 900 patients.2 One large community-based study was excluded because its analysis included patients with multiple episodes of illness;3 treatment group, either antibiotic or placebo, might have confounded the likelihood of suffering a subsequent episode of illness. Original data from this randomized trial have been recovered by the principal investigator (JH), allowing re-analysis of the original study based on those individual patients who suffered from only one episode of illness treated with a single course of antibiotic or placebo.
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Method |
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The methods have been described previously.3 Briefly, in 1969/70, 829 male volunteers aged 20–49 years (out of a total of 2133 registered patients of the same age and sex) registered in two practices in Glasgow were issued with supplies of either demethylchlortetracycline or placebo. They were instructed to take a course of treatment in the event of an acute respiratory illness during a 6-month winter period. Randomization and code for treatment allocation were performed by a pharmaceutical company statistician without knowledge of either investigators or participants. Each participant filled in a diary symptom card for the duration of illness. Individual patient data for single episodes of illness were analysed according to mean duration of illness and resolution of illness at day 7 and day 14.
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Results |
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Of the 829 volunteers, 543 (66%) suffered a respiratory illness, with 301 (36%) suffering one single episode of illness during the 6-month study period. The results of this study are confined to this unconfounded group of patients; details of age and smoking status are presented in Table 1
. The proportion of patients suffering from symptoms of cough, sputum, cough with purulent sputum, or purulent nasal discharge on its own and their median duration of illness are summarized in Table 2. No difference in the mean number of days with symptoms is found when placebo and antibiotic were compared.
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In those 220 (73%) individuals who suffered a cough, 48 (44%) and 19 (17%) of patients taking placebo were still coughing after 1 and 2 weeks, respectively. After adjustment for smoking status, the antibiotic made no difference to resolution of illness at these time periods; adjusted odds ratio 1.2 [95% confidence interval (CI) 0.7–2.1] and 0.8 (95% CI 0.4–1.6), respectively. Smoking had a significantly negative impact on resolution of cough after adjustment for treatment group (mean number of days with cough for smokers 6.7 days versus non-smokers 5.1 days; difference 1.6 days, 95% CI 0.2–3.1 days). Lastly, in the subgroup of patients who suffered cough and purulent sputum (112, 37%), there was a non-significant trend of resolution of symptoms with antibiotic (adjusted odds ratio 0.7, 95% CI 0.5–1.2).
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Discussion |
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The results of this randomized controlled trial, analysed by individual patient and thus unconfounded by the effect of number of courses of treatment taken, provides further evidence that the effect of an antibiotic on resolution of symptoms of minor respiratory illness in normally well adult men aged between 20 and 50 years is likely to be marginal. The results of this study are consistent with the reported resolution of symptoms in most of the other randomized trials of acute respiratory illness in primary care2 and are consistent with the results of this study when analysed by episode of illness.3
Acute respiratory infection describes a continuum of illness severity. Patients with auscultatory abnormalities seem prone to a more protracted illness which usually lasts 3 or 4 weeks.4 No clinical signs were recorded in the patients enrolled into this randomized trial; therefore, the predictive value of symptoms and signs and the subsequent impact of antibiotics cannot be evaluated.
For those patients with both cough and purulent sputum, although no evidence of advantage to antibiotic takers was found, this randomized trial was not sufficiently powered to rule out the possibility of a small but potentially important clinical benefit. Taking the mean resolution of symptoms as 9 days, this study was sufficiently powered to detect just over 1.7 days difference in resolution of symptoms between antibiotic and placebo. Many would argue that a smaller difference between antibiotic and placebo would be clinically important. Against the same assumption of resolution of symptoms in the placebo group, 1324 patients would need to be recruited to detect a difference of half a day between placebo and antibiotic at a significance level of 0.05 and power of 0.8. Thus what is needed are further trials examining whether antibiotics shorten the duration of illness, particularly in higher risk groups such as the elderly.
Once again it seems appropriate to emphasize that the majority of antibiotic prescribing for this clinical syndrome is strongly influenced by patients' expectations of an antibiotic.5,6 Aside from evaluating the efficacy of the antibiotic, further studies which assess management strategies and are aimed at addressing patients' concerns and reducing the prescription of antibiotics are still required.
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References |
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1 Fahey T. Antibiotics for respiratory tract symptoms in general practice. Br J Gen Pract 1998; 48: 1815–1816.[Web of Science][Medline]
2
Fahey T, Stocks N, Thomas T. A quantitative systematic review of randomised controlled trials of acute cough in adults that compare antibiotic with placebo. Br Med J 1998; 316: 906–910.
3 Howie J, Clark G. Double-blind trial of early demethylchlortetracycline in minor respiratory illness in general practice. Lancet 1970; ii: 1099–1102.
4 Verheij T, Hermens J, Kapstein A, Mulder J. Acute bronchitis: course of symptoms and restrictions in patients daily activities. Scand J Prim Health Care 1995; 13: 8–12.[Web of Science][Medline]
5
Macfarlane J, Holmes B, MacFarlane R, Britten N. Influence of patients' expectations on antibiotic management of acute lower respiratory tract illness in general practice: a questionnaire study. Br Med J 1997; 315: 1211–1214.
6 Howie J. Clinical judgement and antibiotic use in general practice. Br Med J 1976; ii: 1061–1064.
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