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

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.

We fully appreciate Dr Furness's comments on the limitations of the definition of asthma based on parents' reports of symptoms and we have contributed on the subject.[1] Epidemiological studies of asthma have to rely on reported symptoms,[2][3] but a better understanding of what parents call wheeze would be of great importance, especially in a multicultural society. The validity of reported asthma symptoms has been demonstrated in adults[4] and the symptoms analysed in the validation were not dissimilar from those used in our study.

We have discussed that parents' perceptions of asthma may vary according to ethnicity and social background.[5][6] False positive and false negative responses could arise if parents mislabel other respiratory symptoms as wheeze or if persistent wheeze is unrecognised.[7] Persistent wheeze is unrecognised as asthma in a large percentage of children from the ethnic minorities and inner city areas. We performed the analysis using either parental reports of persistent wheeze or asthma attacks in order to overcome these differences and the results were consistent. We adjusted for ethnicity and study area in the analysis of the inner city sample to account for the variation in perception.

References
(1) Jones CO, Qureshi S, Rona RJ, et al. Exercise-induced bronchoconstriction by ethnicity and presence of asthma in British nine year olds. Thorax 1996;51:1134-6.

(2) Burney PGJ, Chinn S, Rona RJ. Has the prevalence of asthma increased in children? Evidence from the National Study of Health and Growth 1973-86. BMJ 1990;300:1306-10.

(3) The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Worldwide variations in the prevalence of asthma symptoms: The International Study of Asthma and Allergies in Childhood (ISAAC). Eur Respir J 1998;12:315-35.

(4) Burney PG, Laitinen LA, Perdrizet S, et al. Validity and repeatability of the IUATLD (1984) bronchial symptom questionnaire: an international comparison. Eur Respir J 1989;2:940-5.

(5) Duran-Tauleria E, Rona RJ, Chinn S, Burney P. Influence of ethnic group on asthma treatment in children in 1990-1: national cross sectional study. BMJ 1996;313:148-52.

(6) Duran-Tauleria E, Rona RJ. Geographical and socioeconomic variation in the prevalence of asthma symptoms in English and Scottish children. Thorax 1999;54:476-81.

(7) Cane RS, Ranganathan SC, McKenzie SA. What do parents of wheezy children understand by wheeze? Arch Dis Child 2000;82:327-32.

Dear Editor,

Several measures exist to aid the diagnosis of upper airway obstruction (UAO). These include subjective clinical signs such as the presence of stridor and objective measures such as the pattern of the flow-volume curve. However, by far the simplest and easily measured, but yet relatively unknown and underutilised, is the forced expiratory volume in 1 second (FEV₁) / peak expiratory flow (PEF) ratio. We wish to reignite attention to the use of this uncomplicated measurement through presentation of an interesting clinical case.

A 57-year old lady presented to our respiratory clinic with a complaint of inspiratory stridor. She did not have any other significant respiratory symptoms. There were no overt symptoms of gastroesophageal reflux or oesophageal dysfunction. On direct questioning, she denied any symptoms consistent with collagen vascular disease or vasculitis, except Raynaud’s phenomenon. Her medications included losartan for hypertension and amitriptyline for depression. She is a never-smoker. Clinical examination was unremarkable apart from a soft inspiratory stridor, which was heard best above the suprasternal notch. Her blood biochemistry, haematology, autoimmune, and vasculitic screen were unremarkable. Spirometry showed FEV₁ of 2.79L (110% predicted), forced vital capacity (FVC) of 3.57L (120% predicted), FEV₁/FVC ratio of 78%, and PEF of 396L/min (105% predicted). Her calculated FEV₁/PEF ratio was 7.05ml/L/min. The pattern of the expiratory flow-volume curve was normal with a slight plateau in the inspiratory flow-volume curve (Figure 1). Flexible fibre-optic bronchoscopy demonstrated a subglottic stenosis (Figure 2).

Several pioneering studies have previously determined the usefulness of the FEV₁/PEF ratio in diagnosing UAO.^1-3 FEV₁ is defined as the volume measured during the initial 1 second of a forced expiration from full inspiration and PEF is defined as the maximum flow rate maintained for at least 10 milliseconds during a forced expiration from full inspiration. Therefore, in UAO where the embarrassment is in the pre-carina upper airway, one would intuitively expect the FEV₁/PEF ratio to increase, as chronologically, PEF would be affected more than FEV₁, with the former reflecting more proximal airway per se. Evidently, the FEV₁/PEF ratio has been shown to be significantly higher in patients with UAO compared to patients with asthma, chronic obstructive pulmonary disease, and normal subjects.^1;2 A value of above 10ml/L/min was initially thought to represent UAO,^1;2 although this was subsequently found to vary between 7ml/L/min and 12ml/L/min depending on the different subgroups of UAO such as extrathoracic, fixed, and variable intrathoracic.³

Therefore, although definitive procedures such as flexible fibre-optic bronchoscopy are needed to confirm the diagnosis of UAO, straightforward practical measurements that are useful in day-to-day clinical practice such as the FEV₁/PEF ratio, which is easily obtainable through simple spirometry, may aid in either prompting initial consideration or confirming clinical suspicion of such a diagnosis.

Daniel K C Lee, MB, BCh, MRCP, MD
Prashant S Borade, MB, BS, MD
Nicholas J Innes, MB, BS, FRCP
Department of Respiratory Medicine, Ipswich Hospital, Heath Road, Ipswich IP4 5PD, Suffolk, England, United Kingdom

References

1. Empey DW. Assessment of upper airways obstruction. BMJ 1972; 3: 503-505.
2. Rotman HH, Liss HP, Weg JG. Diagnosis of upper airway obstruction by pulmonary function testing. Chest 1975; 68: 796-799.
3. Mellisant CF, Van Noord JA, Van de Woestijne KP, Demedts M. Comparison of dynamic lung function indices during forced and quiet breathing in upper airway obstruction, asthma, and emphysema. Chest 1990; 98: 77-83.

Figure 1
Expiratory and inspiratory flow-volume curve

Figure 2
Subglottic stenosis found on flexible fibre-optic bronchoscopy