Timothy L Frank

Standards of care for occupational asthma

Occupational asthma remains a common disease in the UK with up to 3000 new cases diagnosed each year. The Health and Safety Executive (HSE) estimates the cost to our society to be over £1.1 billion for each 10-year period.1 In October 2001 the Health and Safety Commission agreed a package of measures aimed at reducing the incidence of asthma caused by exposure to substances in the workplace by 30% by 2010. Key to this aim are primary prevention by proper risk assessment and exposure control, together with secondary prevention to ensure reduction in the delay between the development of allergic symptoms at work (normally nasal or respiratory) and appropriate advice to the affected worker and workplace. Conservative estimates suggest that one in 10 cases of adult onset asthma relate directly to sensitisation in the workplace,2 with a smaller subset of workers with acute irritant induced asthma. The latter—formerly termed reactive airway dysfunction syndrome (RADS)—relates to asthma caused by exposure to high levels of airborne irritants. The prognosis of individuals with occupational asthma is better if they are removed from exposure quickly, particularly within a year of first symptoms.3–5 However, removing individuals often leads to unemployment. If the diagnosis of occupational asthma is incorrect, advising individuals whose asthma is not caused by work to be removed from exposure may have unnecessary financial and social consequences. The intent of this article is not to document the entire current evidence base related to occupational asthma, as the British Occupational Health Research Foundation (BOHRF) recently completed such an evidence review.7 The key points of this article are summarised in box …

Health related quality of life in individuals with asthma related symptoms

BACKGROUND Where evidence is required for disease-area prioritisation (e.g. by national policymakers), impact on health related quality of life (HRQoL) can be considered equitably across diseases using quantitative data from generic HRQoL instruments. Before this can take place, it must be shown that the instrument captures HRQoL impairment associated with each disease area. AIM To ascertain whether the HRQoL impairment associated with respiratory disease can be represented by responses to EQ-5D, a generic HRQoL questionnaire. METHOD EQ-5D and a respiratory health questionnaire were sent to 10,471 adults registered with two general practices in Manchester, UK. EQ-5D examines 5 domains (mobility, self-care, usual activities, pain/discomfort and anxiety/depression) and includes an overall rating via visual analogue scale. Societal valuations of domain responses were also considered. RESULTS HRQoL was substantially reduced in respondents who were likely to have obstructive airways disease (mean EQ-5D(index) 0.63 compared to 0.82, t-test P < 0.001; mean EQ-5D(vas) 62.7 compared to 77.6, t-test P < 0.001) and was negatively associated with respiratory symptoms, older age and female gender. The association with respiratory problems remained following stratification by age and gender. The deficit in HRQoL associated with increasing age was more pronounced in those likely to have obstructive airways disease. CONCLUSION HRQoL measured using EQ-5D is substantially reduced in respondents with respiratory symptoms enabling use of the instrument in inter-disease comparisons.

Long term prognosis in preschool children with wheeze: longitudinal postal questionnaire study 1993-2004.

Objectives To follow a population of preschool children with and without parent reported wheeze over a period of 6-11 years to determine prognosis and its important predictive factors. Design Longitudinal series of five postal surveys based on the international study of asthma and allergies in childhood questionnaire carried out between 1993 and 2004. Setting Two general practice populations, south Manchester. Participants 628 children aged less than 5 years at recruitment and those with at least six years’ follow-up data. Main outcome measures Parent completed questionnaire data for respiratory symptoms and associated features. Results Of 628 children included in the study, 201 (32%) had parent reported wheeze at the first observation (baseline), of whom 27% also reported the symptom on the second occasion (persistent asthma). The only important baseline predictors of persistent asthma were exercise induced wheeze (odds ratio 3.94, 95% confidence interval 1.72 to 9.00) and a history of atopic disorders (4.44, 1.94 to 10.13). The presence of both predictors indicated a likelihood of 53.2% of developing asthma; if only one feature was present this decreased to 17.2%, whereas if neither was present the likelihood was 10.9%. Family history of asthma was not predictive of persistent asthma among children with preschool wheeze. Conclusion Using two simple predictive factors (baseline parent reported exercise induced wheeze and a history of atopic disorders), it is possible to estimate the likelihood of future asthma in children presenting with preschool wheeze. The absence of baseline exercise induced wheeze and a history of atopic disorders reduces the likelihood of subsequent asthma by a factor of five.

Factors influencing the response to postal questionnaire surveys about respiratory symptoms

BACKGROUND Response rates to postal questionnaires have been falling in recent years. AIM To examine factors affecting the response to five postal respiratory questionnaire surveys. DESIGN Cross sectional study. SETTING General practice. METHOD Five surveys were conducted in all adults registered with two UK general practices using an ECRHQ-based questionnaire, with two reminders at 4-week intervals. RESULTS Response rates declined over time (1993 - 71.2%; 1995 - 70.5%; 1999 - 65.5%; 2001 - 65.3%; 2004 - 46.9%). Age and gender of non-responders were available for 2001 and 2004: responders were older (mean 48.8 years vs 37.6, p<0.001; 50.5 vs 38.8, p<0.001) and more likely to be female (54.9% vs 44.9%, p<0.001; 55.3% vs 48.5%, p<0.001). The response rate was increased by 18% (2004) and 23% (2001) by the use of two reminders. Early responders were older and more likely to be females, but were less likely to smoke than late responders after reminders. There was no important association between respiratory symptoms and associated feature prevalence and stage of response. CONCLUSION Declining response rates may represent reduced motivation and reluctance to share personal information. Qualitative exploration of late/non-response could help reduce bias when planning and analysing such surveys. The use of two reminders is an important factor in improving response.

Standards of care for occupational asthma: an update

Background The British Thoracic Society (BTS) Standards of Care (SoC) Committee produced a standard of care for occupational asthma (OA) in 2008, based on a systematic evidence review performed in 2004 by the British Occupational Health Research Foundation (BOHRF). Methods BOHRF updated the evidence base from 2004–2009 in 2010. Results This article summarises the changes in evidence and is aimed at physicians, nurses and other healthcare professionals in primary and secondary care, occupational health and public health and at employers, workers and their health, safety and other representatives. Conclusions Various recommendations and evidence ratings have changed in the management of asthma that may have an occupational cause.

Smoking, respiratory symptoms and likely asthma in young people: evidence from postal questionnaire surveys in the Wythenshawe Community Asthma Project (WYCAP)

BackgroundAlthough it is recognised that smoking is a major risk factor for subjects with chronic obstructive pulmonary disease and is associated with respiratory symptoms, there is less agreement concerning the relationship between asthma and smoking. This study aims to examine the relationship between cigarette smoking and asthma prevalence.MethodData were used from two postal questionnaire surveys (1999 and 2001) in two general practice populations, using a respiratory questionnaire based on the ECRHQ and a generic quality of life questionnaire (EQ-5D). Only subjects less than 45 years old were included in the survey. An empirical definition of likely asthma was used based on respiratory questionnaire responses. Smoking was examined according to three categories, current smoker, ex smoker and never smoker.ResultsAlmost 3500 subjects were included in the analyses. Current smokers had a higher prevalence of likely asthma compared to never smokers, odds ratio (OR) 1.59 (95% confidence interval (CI) 1.24 to 2.04). and also compared to ex smokers OR 1.79 (CI 1.25 to 2.56), but there was no difference between ex smokers and never smokers (OR 1.00 (0.75–1.35)). Current smoking was also positively associated with all symptoms but not with a history of hayfever/eczema.ConclusionAlthough the positive association found between current smoking and obstructive airways disease is likely to be due to the effect of cigarettes on asthma, it could reflect an association with early COPD (GOLD stages 0 or 1). Smoking cessation has a beneficial effect on the prevalence of respiratory symptoms and is therefore of paramount importance among these young adults.

Using a Neural Network to Screen a Population for Asthma

PURPOSE To use a neural network to rank a population according to individual likelihood of asthma based on their responses to a respiratory questionnaire. METHODS A final diagnosis of asthma can be made only after full clinical assessment but limited resources make it impossible to offer this to complete populations as part of a screening programme. Prioritisation is required so that review can be offered most promptly to those most in need. A stratified random sample of 180 from 6825 respondents to a community survey underwent clinical review. They were categorised according to likelihood of asthma by three independent experts whose opinions were combined into a single probability label for each patient. A neural network was trained to relate questionnaire responses to probability labels. The trained network was applied to the whole community to produce a ranking order based on likelihood of asthma. A screening threshold could then be set to correspond to available resources, and patients above this level with no recorded evidence of asthma diagnosis could be assessed clinically. Using the known probability labels from the training set, it was possible to derive the expected proportion of true asthmatics in any set of patients. RESULTS If the screening threshold had been set to capture the top 10% of the ranked population (n = 683), then 239 patients above this threshold had no evidence of diagnosis and would need assessment. Of these, it would be expected that 74% would have the diagnosis confirmed. CONCLUSIONS This approach allows prioritisation of a population where resources for diagnostic examination are limited.

Temporal change in health-related quality of life: a longitudinal study in general practice 1999–2004

BACKGROUND In order to assess and plan for changing healthcare needs, the lack of available information regarding temporal changes in the health-related quality of life of a population must be addressed. AIM This paper aims to describe such changes over 5 years in a general population. DESIGN OF STUDY Longitudinal postal questionnaire study. SETTING UK general practice. METHOD This was a longitudinal postal questionnaire study in two general practice populations, using the generic instrument EQ-5D to measure health-related quality of life. Individuals were included if they responded to three postal surveys in 1999, 2001, and 2004 and there were three consecutive values of EQ-5D(index) available between 1999 and 2004. RESULTS A total of 2498 subjects were included in the study. After adjustment for potential confounders (including ageing), health-related quality of life declined significantly over the observation period. The change in EQ-5D(index) was from 0.79 to 0.74 and for EQ-5D(vas) 76.8 to 73.3 (P for both trends <0.001). CONCLUSION Health-related quality of life deteriorated in these populations over 5 years. In an era of improvements in mortality, this has important implications for the use of health-related quality of life data in healthcare planning and resource allocation.

Identification of adults with symptoms suggestive of obstructive airways disease: validation of a postal respiratory questionnaire.

BackgroundTwo simples scoring systems for a self-completed postal respiratory questionnaire were developed to identify adults who may have obstructive airways disease. The objective of this study was to validate these scoring systems.MethodA two-stage design was used. All adults in two practice populations were sent the questionnaire and a stratified random sample of respondents was selected to undergo full clinical evaluation. Three respiratory physicians reviewed the results of each evaluation. A majority decision was reached as to whether the subject merited a trial of obstructive airways disease medication. This clinical decision was compared with two scoring systems based on the questionnaire in order to determine their positive predictive value, sensitivity and specificity.ResultsThe PPV (positive predictive value) of the first scoring system was 75.1% (95% CI 68.6–82.3), whilst that of the second system was 82.3% (95% CI 75.9–89.2). The more stringent second system had the greater specificity, 97.1% (95% CI 96.0–98.2) versus 95.3% (95% CI 94.0–96.7), but poorer sensitivity 46.9% (95% CI 33.0–66.8) versus 50.3% (95% CI 35.3–71.6).ConclusionThis scoring system based on the number of symptoms/risk factors reported via a postal questionnaire could be used to identify adults who would benefit from a trial of treatment for obstructive airways disease.

Prevalence of respiratory symptoms, features of asthma, and characteristics associated with respiratory disease, in 6-11 year olds in Manchester

AIMS This paper describes the prevalence of respiratory symptoms, features of asthma, and characteristics associated with respiratory disease in 6-11 year old children in an historical cohort study. METHODS The study included 5086 children, all born in the same maternity unit in the north west of England over a four-year period. The prevalence of respiratory symptoms, features of asthma, and characteristics associated with respiratory disease were determined by the use of parent-completed questionnaires. Skin prick tests were used to ascertain atopic status. RESULTS The response was 47.5%. The prevalence of wheeze, asthma medication use and atopic sensitisation were 20.3%, 16.2% and 37.1% respectively. Wheeze and atopy were significantly more prevalent in boys (22.4% versus 17.9% and 43.0% versus 29.3%, respectively). CONCLUSIONS This study identified a high prevalence of respiratory disease in this population and provides a baseline for monitoring trends in respiratory disease in 6-11 year old children.