I read with great interest the article of Nakayama et al about tuberculin responses and risk of pneumonia in immobile elderly patients. It is known that TH1 cells are important in delayed type hypersensitivity responses to tuberculin. The authors' findings are important in assessment of pathogenesis of pneumonia in elderly patients. But I have some doubts about the analysis of data. The groups were compared by using Student's t test although the groups were less than 30. So Mann Whitney U test must be used instead of Student t test.

The observational data presented by Macfarlane et al on the aetiology of acute lower respiratory tract illness in the community[1] confirm that the often stated assertion that these illnesses are usually caused by viral infection is incorrect. The high prevalence of bacteriological and atypical pathogens, and in particular the high prevalence of C pneumoniae in these patients is of interest and points to the need for further studies to clarify the clinical significance of these isolates. The lack of correlation between indirect evidence of infection (radiographic and CRP levels), GP assessment of the need for antibiotics and pathogen isolation are also of great interests and have important messages for those working in the community. The outcome conclusions from this study do however need to be treated with some caution.

The authors state that outcomes were similar whether or not antibiotics were used, but as this was an unrandomised observational study, we cannot say that the groups of patients who were and were not given antibiotics by the GPs in the study were comparable. The experienced GP researchers in this study may well have had particular reasons for giving or withholding antibiotics, and the significance of similar reconsultation rates in these groups is open to interpretation.

In the accompanying editorial,[2] the authors state that systematic reviews of randomised controlled trials of antibiotic prescription for acute bronchitis do not support antibiotic treatment, and evidence based educational initiatives aimed at GPs are advocated as one of the strategies to alter clinical behaviour.

Having recently reviewed the literature on this important clinical topic myself,[3] I cannot agree with their assessment of the current evidence. The more recent review they quote[4] has been criticised on methodological grounds, and the most recent and extensive systematic review of this clinical problem, published on the Cochrane database,[5] comes to 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.

The world literature currently consists of eight randomised controlled trials of variable quality, some 20 years old, that use different antibiotic regimens and different outcome measures. Several of these studies have concluded that the antibiotic regimens used did improve outcomes.

The recent enquiry into community acquired pneumonia deaths in young adults published in this journal,[6] revealed that the primary care management of these patients at the severe end of lower respiratory tract infection spectrum was deficient in many cases - three quarters of patients had seen their GP for the illness without a correct diagnoses and few had received antibiotics from their GP. There are many areas of uncertainty remaining in this field, and while observational studies such as this help to bring some clarity into this confused area of daily clinical practice, well designed randomised controlled trials are still needed to produce the evidence based guidance that GPs require. The current evidence is inadequate to meet the challenge identified by Macfarlane et al,[1] that of identifying the cohort of patients who will benefit from antibiotics.

Dr Mike Thomas
Clinical Research Fellow
Department of Primary Care Respiratory Medicine
University of Aberdeen, UK

References
(1) Macfarlane J, Holmes W, Gard P, Macfarlane R, Rose D, Weston V. et al. Prospective study of the incidence, aetiology and outcome of lower respiratory tract illness in the community. Thorax 2001;56:109-14.

(2) Steele K, Gormley G, Webb CH. Management of adult lower respiratory tract infection in primary care. Thorax 2001;56:88.

(3) Thomas M. The management of acute respiratory tract infection in adults in primary care. Primary Care Respiratory Journal 200;9:4-7.

(4) Fahey T, Stocks N, Thomas T. Quantitative systematic review of randomised controlled trials comparing antibiotic with placebo for acute cough in adults. BMJ 1998;316:910.

(5) Becker L, Glazier R, McIsaac W, and et al. Antibiotics for acute bronchitis. Douglas R, Bridges-Webb C, Glasziou P, and et al. (1). 1998. Oxford, Update software. Acute Respiratory Infections Module of the Cochrane database of systematic reviews.

(6) Simpson JCG, Macfarlane JT, Watson J, Woodhead M. A national confidential enquiry into community acquired pneumonia deaths in young adults in England and Wales. Thorax 2000;55:1040-5.

I read with interest this article in Thorax and have been worried by the comments in "Pulse" which followed (9 December 2000).

The lack of information about the general practitioner (GP) consultations, and the non- availability of records is alarming and dispiriting. Particularly when nowadays much information is computerised and records can in emergency situations, given the hard work of Health Authorities pass between practices in days.

It would be helpful to know what physical signs might have been missed, indeed the selection process does not define presenting clinical signs (beyond absence of life). So we have no denominator of cases where we might need to think harder to avoid these events. As an habitual "examiner" after ten years in general practice (and ten in hospital medicine) I have been surprised by the paucity of physical signs in patients with cough fever and purulent sputum. In these days of evidenced based guidelines leading us away from the use of antibiotics we need something hard to guide us to avoid the tragic but extremely rare cases described.

It is a sad fact that subtle physical signs can be missed - even if they are indeed present. Ten years in general practice has taught me that serious illness changes quickly from minor symptoms to dire straits. The only similar case in my recollection was a young woman sent home from casualty to return moribund to hospital the same day with lobar pneumonia.

Steven Stern, MB ChB BSc MRCP
Principal in General Practice