Occupational asthma in New South Wales (NSW): a population-based study

BACKGROUND

The proportion of asthma in adults that is due to occupational exposures is not known.

AIM

To examine the contribution of workplace exposures to the development of asthma in adults in New South Wales (NSW) in a cross sectional, population-based study.

METHODS

A randomly selected population of 5,331 18- to 49-year olds completed and returned a mailed questionnaire (response rate 37%). In adult-onset asthmatics we examined the association of asthma with reported exposure, within 1 year of asthma onset, to a list of occupations and exposures known to be at risk for occupational asthma (high-risk jobs and exposures).

RESULTS

Among 910 subjects (18%) with asthma, 383 (7%) subjects reported adult-onset disease. After adjusting for sex, age and smoking, working in any high-risk job or exposure at the time of asthma onset was significantly associated with adult-onset asthma (OR 1.51, 95% CI 1.19-1.92). The population attributable risk (PAR) of adult-onset asthma for either a high-risk job or an exposure was 9.5%. Sudden onset, irritant or reactive airways dysfunction syndrome type exposures were associated with adult-onset asthma (OR 4.65, 95% CI 1.64-13.2). The PAR of adult-onset asthma for these exposures was 0.2%.

CONCLUSION

Reported adult onset of asthma is common and occupational exposures may be associated with 9.5% of prevalent cases of adult-onset asthma in NSW.

Anxiety, panic and adult asthma: a cognitive-behavioral perspective

A review of previous research suggests increased probability of the prevalence of anxiety disorders, and particularly panic disorder and panic attacks in patients with asthma, as compared to a normal population. Research also indicates significant levels of co-morbidity between asthma and anxiety as measured on dimensional scales of anxiety and panic. Clinical anxiety and panic manifestations affect symptom perception and asthma management through the effects of anxiety symptoms such as hyperventilation, and indirectly through self-management behavior and physician response. However, there is limited data on the impact of anxiety co-morbidity on asthma quality of life. Some studies indicate that individuals with co-morbid asthma and anxiety or panic report worse asthma quality of life both in general and in relation to their symptomatology, being limited in their daily activities, in response to environmental stimuli and in regard to feelings of emotional distress. Cognitive-behavioral therapy (CBT) is an effective and empirically supported treatment of choice for anxiety disorders and panic attacks. However, standard CBT protocols for anxiety and panic may need to be specifically targeted at improving asthma outcomes. Also, asthma research literature is lacking in randomized controlled trials applying CBT to patients with co-morbid asthma and clinical anxiety manifestations. Trials evaluating CBT interventions in individuals with clinical anxiety manifestations and asthma may provide evidence of these interventions as an effective adjunct to improve asthma management and control.

Exasperations" of asthma: a qualitative study of patient language about worsening asthma

OBJECTIVES

To identify expressions used by patients to describe worsening asthma; to examine the relevance of the word "exacerbation" to patients' experience; and to investigate whether their language is influenced by the severity of the episode and/or the target audience such as family members, friends and work colleagues.

DESIGN AND SETTING

Qualitative study carried out from 1 January to 30 December 2004 among community volunteers to a research institute. Semistructured face-to-face interviews were used to elicit descriptions of episodes of worsening asthma, and further questioning was used to examine language used with family, employer and doctor.

PARTICIPANTS

25 people with asthma, aged 22-75 years.

MAIN OUTCOME MEASURE

Themes identified by open coding about patient language for worsening asthma.

RESULTS

12 participants were not familiar with "exacerbation" and only three would use it themselves. "Attack" was the only specific term spontaneously volunteered (20 participants), but it was used for anything from mild to life-threatening episodes. Patients often downplayed the severity of worsening asthma to their families. Different language was used with employers, sometimes to justify sick leave and sometimes because of fear of perceived discrimination. When communicating with clinicians about worsening asthma, patients used symptom descriptors rather than specific terms.

CONCLUSION

There are important differences in the language patients and clinicians use to describe worsening asthma, and the word "exacerbation" has poor utility for communication with patients.

Variance components analyses of multiple asthma traits in a large sample of Australian families ascertained through a twin proband

BACKGROUND

Intermediate phenotypes are often measured as a proxy for asthma. It is largely unclear to what extent the same set of environmental or genetic factors regulate these traits.

OBJECTIVE

Estimate the environmental and genetic correlations between self-reported and clinical asthma traits.

METHODS

A total of 3,073 subjects from 802 families were ascertained through a twin proband. Traits measured included self-reported asthma, airway histamine responsiveness (AHR), skin prick response to common allergens including house dust mite (Dermatophagoides pteronyssinus [D. pter]), baseline lung function, total serum immunoglobulin E (IgE) and eosinophilia. Bivariate and multivariate analyses of eight traits were performed with adjustment for ascertainment and significant covariates.

RESULTS

Overall 2,716 participants completed an asthma questionnaire and 2,087 were clinically tested, including 1,289 self-reported asthmatics (92% previously diagnosed by a doctor). Asthma, AHR, markers of allergic sensitization and eosinophilia had significant environmental correlations with each other (range: 0.23-0.89). Baseline forced expiratory volume in 1 s (FEV(1)) showed low environmental correlations with most traits. Fewer genetic correlations were significantly different from zero. Phenotypes with greatest genetic similarity were asthma and atopy (0.46), IgE and eosinophilia (0.44), AHR and D. pter (0.43) and AHR and airway obstruction (-0.43). Traits with greatest genetic dissimilarity were FEV(1) and atopy (0.05), airway obstruction and IgE (0.07) and FEV(1) and D. pter (0.11).

CONCLUSION

These results suggest that the same set of environmental factors regulates the variation of many asthma traits. In addition, although most traits are regulated to great extent by specific genetic factors, there is still some degree of genetic overlap that could be exploited by multivariate linkage approaches.

Robust estimation of experimentwise P values applied to a genome scan of multiple asthma traits identifies a new region of significant linkage on chromosome 20q13

Over 30 genomic regions show linkage to asthma traits. Six asthma genes have been cloned, but the putative loci in many linked regions have not been identified. To search for asthma susceptibility loci, we performed genomewide univariate linkage analyses of seven asthma traits, using 202 Australian families ascertained through a twin proband. House-dust mite sensitivity (Dpter) exceeded the empirical threshold for significant linkage at 102 cM on chromosome 20q13, near marker D20S173 (empirical pointwise P = .00001 and genomewide P = .005, both uncorrected for multiple-trait testing). Atopy, bronchial hyperresponsiveness (BHR), and forced expiratory volume in 1 s (FEV1) were also linked to this region. In addition, 16 regions were linked to at least one trait at the suggestive level, including 12q24, which has consistently shown linkage to asthma traits in other studies. Some regions were expected to be false-positives arising from multiple-trait testing. To address this, we developed a new approach to estimate genomewide significance that accounts for multiple-trait testing and for correlation between traits and that does not require a Bonferroni correction. With this approach, Dpter remained significantly linked to 20q13 (empirical genomewide P = .042), and airway obstruction remained linked to 12q24 at the suggestive level. Finally, we extended this method to show that the linkage of Dpter, atopy, BHR, FEV1, asthma, and airway obstruction to chromosome 20q13 is unlikely to be due to chance and may result from a quantitative trait locus in this region that affects several of these traits.

Repeatability of peak nasal inspiratory flow measurements and utility for assessing the severity of rhinitis

BACKGROUND

The measurement of peak nasal inspiratory flow (PNIF) provides a simple, cheap, fast and readily available tool for determining the extent of nasal airway patency. However, there are questions regarding its repeatability when used to assess the degree of nasal obstruction in large populations. Therefore, this study aimed to evaluate the repeatability of PNIF measurements and to assess their association with the signs and symptoms of rhinitis.

METHODS

The PNIF, rhinitis symptoms, judged by Meltzer questionnaire and rhinitis signs, as determined by anterior rhinoscopy, were assessed in 283 adults representative of the general population. One training and two test PNIF measurements were recorded during the same session.

RESULTS

The PNIF was highly reproducible (ICC = 0.92; 95% limits of agreement: +/-36 l/min). The PNIF was strongly correlated with rhinitis signs, measured by anterior rhinoscopy (rs= -0.38, P < 0.0001) but was not correlated with rhinitis symptoms, measured by questionnaire (rs= -0.11, P = 0.057). Differences in PNIF for subjects categorized as asymptomatic, mild or moderate/severe on the basis of rhinitis signs, were highly significant (P < 0.0001), but less significant on the basis of rhinitis symptoms (P = 0.04). A PNIF cut-off of 115 l/min had moderately high specificity (72%) and sensitivity (65%) and a high negative predictive value (90%) for moderate/severe signs of rhinitis.

CONCLUSION

In a large general population-based sample of young adults, PNIF was highly reproducible and closely related to the signs of rhinitis, as determined by clinical examination. The PNIF provides information that is qualitatively different to that provided by symptom scores and may be useful to measure the extent of nasal obstruction.

The burden of asthma in children: an Australian perspective

The burden of asthma among children is high in Australia compared with many other countries. Recent data show that 14-16% of children report a diagnosis of asthma that remains a problem. Boys, children under the age of 5 years and urban indigenous children experience a greater burden of asthma than other children. More than one-third of children with asthma have sleep disturbance due to the illness and 60% have missed school and/or experienced other restrictions in their activities due to the disease. Despite this, there is continuing evidence of under-utilisation of effective treatment for the disease. Asthma is a major cause of healthcare utilisation among children. Since the early 1990s, there has been a decline in both hospitalisation rates and general practitioner consultation rates for asthma among children. It remains to be seen whether this favourable trend will continue and extend into the adult age range.

Effects of gas and other fume emitting heaters on the development of asthma during childhood

BACKGROUND

Several studies have shown adverse effects of gas cookers and heaters on respiratory health. The long term effects of early life exposure to these appliances are not known. This study investigated the effect of exposure to fume emitting heaters, currently and during the first year of life, on the risk of asthma outcomes.

METHODS

A cross sectional study of schoolchildren (n = 627) aged 8-11 years was conducted in Belmont, Australia. Information on symptoms and heating types was collected by parent completed questionnaire. Atopy was assessed by skin prick tests and airway hyperresponsiveness (AHR) was assessed by histamine challenge test.

RESULTS

There was no association between the current use of fume emitting heaters and any of the asthma outcomes. However, having been exposed to fume emitting heaters during the first year of life was associated with an increased risk of having AHR (relative risk (RR) 1.47, 95% confidence interval (CI) 1.06 to 2.03), recent wheeze (RR 1.44, 95% CI 1.11 to 1.86), and recent wheeze + AHR (RR 2.08, 95% CI 1.31 to 3.31).

CONCLUSION

If confirmed in other settings, this finding would require a review of the range of heating types that are appropriate for use in households in which young children live.

Presence and timing of cat ownership by age 18 and the effect on atopy and asthma at age 28

BACKGROUND

Asthma and allergic sensitization to cats frequently coexist, although recent studies show less atopic disease among people who had pets in infancy. However, no longterm evaluations have been performed thus far.

OBJECTIVE

We sought to evaluate the relationship between cat ownership at different age periods (< 18, > 18, and both periods and atopic disease at age 28.

METHODS

Australian school children aged 8 to 10 years were recruited in 1982 and participated in follow-up surveys until 2002. Cat ownership was defined by surveys in 1992 and 2002 as having a cat before age 18 only, after age 18 only, or in both periods of life. Health outcomes were defined at a mean age of 28.5 years.

RESULTS

Complete data were available for 224 subjects, 50 of whom had a cat before 18 years of age only, 14 after age 18 only, and 70 in both periods. Compared with 90 subjects that never had a cat, having a cat before age 18 protected against atopy to outdoor allergens, airway hyperresponsiveness (AHR) to histamine, current wheeze, and current asthma (P < .05). In contrast, subjects who acquired their first cat after age 18 showed a trend toward higher prevalence rates for asthma symptoms and AHR (P > .10).

CONCLUSIONS

Having had a cat before 18 years of age protects against adult asthma and atopy.

Childhood factors that predict asthma in young adulthood

Predicting adult asthma, using childhood characteristics, is important for advising on prognosis and, potentially, for secondary prevention. A novel use of multivariate likelihood ratios (LRs) to quantify prognosis is described here. Of 718 subjects of a community-based cohort, 575 (80%) members were recruited at age 8-10 yrs and were re-assessed 15-17 yrs later. At baseline, information about symptoms, spirometry, histamine challenge and skin-prick tests were collected. At follow-up "asthma symptoms" were defined as wheeze, sleep disturbance from asthma or inhaled steroid use within the previous year. LRs were calculated for significant predictors of this outcome. Shinkage factors were applied to yield multivariate LRs. Childhood characteristics that independently predicted asthma symptoms in adulthood were obstructive spirometry (adjusted (adj)LR 2.9, 95% confidence interval (CI) 1.3-6.5), airway hyperresponsiveness (adjLR 2.6, 95% CI 1.8-3.7), atopy (adjLR 2.0, 95% CI 1.5-2.7), recent wheeze (adjLR 1.9, 95% CI 1.5-2.5) and being female (adjLR 1.29, 95% CI 0.8-2.1). Children with all five characteristics had a cumulative LR of 36.9 for asthma symptoms in adulthood. Most adults who had asthma symptoms did not have manifestations of asthma as children. However, the presence of obstructive spirometry, airway hyperresponsiveness and atopy in childhood identifies individuals with increased likelihood of having asthma in adulthood. Cumulative likelihood ratios are more valuable than odds ratios for quantifying risk in individuals and for identifying people with most to gain from preventive interventions.

Written individualised management plans for asthma in children and adults

BACKGROUND

Non-adherence to treatment advice is a common phenomenon in asthma and may account for a significant proportion of the morbidity. Comprehensive care that includes asthma education, a written self-management plan and regular review has been shown to improve asthma outcomes, but the contribution of these components has not been established.

OBJECTIVES

To determine whether the provision of a written asthma self-management plan increases adherence and improves outcome.

SEARCH STRATEGY

We carried out a search on the Cochrane Airways Group trials register. There was no language restriction. The search of the databases used the following terms: action plan OR self OR self-care OR self-manag* OR educ* AND adher* OR comply OR compli*. We contacted authors of included studies for any unpublished or on-going studies and bibliographies of all included studies and reviews were searched for further studies. The most recent search was carried out in May 2003.

SELECTION CRITERIA

We only considered randomised controlled trials (RCTs) in patients with asthma. Participants must have been assigned to receive an individualised written asthma management plan (symptom or peak flow based) about the actions required for regular asthma management and/or the actions to take in the event of an asthma exacerbation.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed study quality and abstracted data.

MAIN RESULTS

Seven trials met the inclusion criteria. The written management plans were either peak flow or symptom based, which were compared against each other or compared to no written management plan. Reported outcomes included: medication adherence, hospitalisation, emergency department visits, oral corticosteroid use, lung function, days lost from school/work, unscheduled doctor visits and respiratory tract infections. There was no consistent evidence that written plans produced better patient outcomes than no written plan. For some outcomes, there appeared to be an advantage of one type of plan over the other, but there was no consistency - one type of plan was not consistently more effective than another.

REVIEWERS' CONCLUSIONS

The available trials are too small and the results too few and inconsistent to form any firm conclusions as to the contribution of written self management plans in the known beneficial effects of a comprehensive asthma care programme.

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

The effect of neonatal BCG vaccination on atopy and asthma at age 7 to 14 years: an historical cohort study in a community with a very low prevalence of tuberculosis infection and a high prevalence of atopic disease

BACKGROUND

There are conflicting reports on the effect of BCG vaccination on the subsequent development of atopy and asthma. There are no data on the effects of neonatal BCG vaccination on cytokine responses of lymphocytes that are exposed in vitro to allergens.

OBJECTIVES

We sought to test the hypothesis that neonatal BCG vaccination or, alternatively, evidence of an immunologic memory of this vaccination is associated with a reduced prevalence of allergic sensitization, asthma, eczema, and hay fever during childhood.

METHODS

An historical cohort study was conducted among 7- to 14-year-old children who were born in 2 districts in Sydney, Australia, and whose mothers were born in southeast Asia. One district had routinely administered BCG vaccination to infants born to overseas-born mothers and the other had not. Eligible subjects were identified from birth registers. Consenting subjects completed questionnaires, performed spirometric and airway hyperresponsiveness testing, and had allergen skin prick testing and tuberculin skin testing. Blood was collected to measure total serum IgE levels and for in vitro lymphocyte culture in the presence of an extract of house dust mite, the dominant allergen in this region, and purified protein derivative of Mycobacterium tuberculosis (tuberculin). IL-4, IL-5, IL-10, and IFN-gamma were measured in the culture supernatant.

RESULTS

The cohort included 309 BCG-vaccinated subjects and 442 non-BCG-vaccinated subjects. BCG-vaccinated subjects did not have a lower rate of allergic sensitization than nonvaccinated subjects. However, among the subgroup of subjects with a family history of rhinitis or eczema, BCG vaccination was associated with a lower prevalence of current asthma (defined as recent wheezing plus airway hyperresponsiveness; relative risk, 0.46; 95% CI, 0.22-0.95). BCG vaccination was also associated with lower levels of allergen-stimulated IL-10 production in vitro. Among the BCG-vaccinated subjects, the 44 (14.3%) who had tuberculin skin test reaction sizes of 5 mm or greater and the 31 (18.3%) who demonstrated an in vitro IFN-gamma response to purified protein derivative of M tuberculosis did not have lower rates of allergic sensitization and, overall, did not have a lower prevalence of allergic disease than tuberculin skin test or IFN-gamma nonreactors.

CONCLUSION

We conclude that neonatal BCG vaccination has an effect on T-cell allergen responsiveness 7 to 14 years after vaccination and that among a subgroup of subjects with an inherited predisposition to allergic disease, this is associated with clinically relevant beneficial effects. The findings of this study encourage the view that external influences on the immune system in the neonatal period have consequences that extend into later childhood and influence the expression of asthma. Genetic factors are likely to modify the effect of those external factors.

Use of a paper disposable cup as a spacer is effective for the first-aid management of asthma

OBJECTIVE

There are many settings in which a spacer device is not available for the administration of bronchodilator. Therefore, we tested whether a paper disposable cup is as effective as a commercially produced spacer to administer bronchodilator.

METHODOLOGY

Randomised controlled trial. 50 subjects aged 16-50 years who had wheeze and a greater than 10% decrease in FEV1 after histamine inhalation test (HIT). Subjects were randomised to either the 150 ml paper disposable cup group (CUP) or the commercially produced spacer group (SPACER). Twenty minutes after 400 microg salbutamol was administered FEV1 was measured. The recovery index measured post-bronchodilator FEV1 as a percentage of baseline FEV1. Also, analysis of covariance tested whether recovery of FEV1 was related to the magnitude of the fall following the HIT.

RESULTS

There were no statistically significant differences between CUP and SPACER groups in any characteristics. There was no difference for the recovery index (t48=1.14, P=0.26). Regression analyses showed that the relation between the magnitude of the fall in FEV1 during the HIT and the percent recovery was not different between the CUP and SPACER groups (t=-1.2, P<0.23).

CONCLUSIONS

A paper disposable cup was effective for the reversal of mild to moderate bronchoconstriction. Therefore, a paper disposable cup can be used for the first-aid management of asthma when there is concern about cross-infection and a commercially produced spacer is not available.

Subject discomfort associated with the histamine challenge in a population study

BACKGROUND

Many review articles report the safety and lack of serious side-effects associated with the histamine challenge. Even though methacholine and hypertonic saline are more commonly used to measure airway responsiveness, histamine challenges are used in many countries around the world. Levels of subjects discomfort after a challenge have not been quantified. This study quantified the incidence, severity and duration of subject discomfort after histamine challenge.

METHODS

Ninety-nine subjects were recruited in an Australian multi-centre population-based study of the genetic epidemiology of asthma. Subjects completed a histamine challenge with final cumulative dose 3.2 micromol. Immediately, and 10 min, after challenge subjects rated their discomfort for cough, headache, throat irritation, hoarse voice and flushed. Research personnel also reported their perception of subjectdiscomfort.

RESULTS

Subjects and research personnel reported a small degree of subject discomfort for all symptoms immediately after the histamine challenge. Overall, median symptom scores were less than 1.5 out of 10. Discomfort scores improved 10 min after challenge and cough, throat irritation and flushed improved significantly

CONCLUSIONS

This study confirms the tolerability of the histamine challenge.

Particulate masks and non-powdered gloves reduce latex allergen inhaled by healthcare workers

BACKGROUND

Although allergy to latex is a well-characterized phenomenon, some hospitals continue to provide staff with powdered latex gloves as an option to low- or non-powdered gloves.

OBJECTIVE

We aimed to measure the extent to which inhalation of latex particles could be reduced by the use of protective masks or by replacing powdered latex gloves with non-powdered latex gloves.

METHODS

Twenty healthcare workers in a hospital setting wore nasal air samplers (NAS) and Institute of Occupational Medicine (IOM) samplers for four 20-min periods. Subjects wore powdered gloves, non-powdered gloves and no gloves during three sampling periods, and in the fourth, subjects applied an aerosol barrier face-mask or a particulate face-mask (N95) while wearing powdered gloves. All samples were stained for particles bearing Hev b 5 allergen by the Halogen assay.

RESULTS

All subjects inhaled Hev b 5 bearing particles in all sampling periods. IOM samplers collected particles at 70% of the rate of NAS. The number of particles inhaled while wearing powdered gloves was 23.8-fold higher than when not wearing gloves and 9.7-fold higher than when wearing non-powdered latex gloves (P < 0.0001). Wearing an aerosol barrier mask did not significantly reduce the number of particles inhaled (P = 0.108), while use of particulate masks significantly reduced the number of particles inhaled by 17.4-fold (P = 0.003).

CONCLUSIONS

Use of non-powdered gloves is the most effective method of reducing occupational aeroallergen exposure to latex arising from gloves. However, secondary protection using particulate masks is a valid alternative, and may be helpful for preventing respiratory sensitization.

Risk factors for onset and remission of atopy, wheeze, and airway hyperresponsiveness

BACKGROUND

Although many children with asthma may have a remission as they grow and other children who did not have asthma may develop asthma in adult life, knowledge about the factors that influence the onset and prognosis of asthma during adolescence and young adulthood is very limited.

METHODS

A cohort of 8-10 year old children (n=718) living in Belmont, New South Wales, Australia were surveyed six times at 2 yearly intervals from 1982 to 1992, and then again 5 years later in 1997. From this cohort, 498 subjects had between three and seven assessments and were included in the analysis. Atopy, airway hyperresponsiveness (AHR), and wheeze in the last 12 months were measured at each survey. Late onset, remission, and persistence were defined based on characteristics at the initial survey and the changes in characteristics at the follow up surveys.

RESULTS

The proportion of subjects with late onset atopy (13.7%) and wheeze (12.4%) was greater than the proportion with remission of atopy (3.2%) and wheeze (5.6%). Having atopy at age 8-12 years (OR 2.8, 95% CI 1.5 to 5.1) and having a parental history of asthma (OR 2.0, 95% CI 1.02 to 4.13) were significant risk factors for the onset of wheeze. Having AHR at age 8-12 years was a significant risk factor for the persistence of wheeze (OR 4.3, 95% CI 1.3 to 15.0). Female sex (OR 1.9, 95% CI 1.01 to 3.60) was a significant risk factor for late onset AHR whereas male sex (OR 1.9, 95% CI 1.1 to 2.8) was a significant risk factor for late onset atopy.

CONCLUSIONS

The onset of AHR is uncommon during adolescence, but the risk of acquiring atopy and recent wheeze for the first time continues during this period. Atopy, particularly present at the age of 8-10 years, predicts the subsequent onset of wheeze.

Written individualised management plans for asthma in children and adults

BACKGROUND

Non-adherence to treatment advice is a common phenomenon in asthma and may account for a significant proportion of the morbidity. Comprehensive care that includes asthma education, written self-management plan and regular review has been shown to improve asthma outcomes, but the contribution of these components has not been established.

OBJECTIVES

To determine whether the provision of a written asthma self-management plan increases adherence and improves outcome.

SEARCH STRATEGY

A search was carried out on the Cochrane Airways Group trials register. There was no language restriction. The search of the databases used the following terms: action plan OR self OR self-care OR self-manag* OR educ* AND adher* OR comply OR compli*. Authors of included studies were contacted for any unpublished or on-going studies and bibliographies of all included studies and reviews were searched for further studies.

SELECTION CRITERIA

Only randomised controlled trials (RCTs) in patients with asthma were considered. Participants must have been assigned to receive an individualised written asthma management plan (symptom or peak flow based) about the actions required for regular asthma management and/or the actions to take in the event of an asthma exacerbation.

DATA COLLECTION AND ANALYSIS

Study quality was assessed and data abstracted by two reviewers independently.

MAIN RESULTS

Six trials met the inclusion criteria. The written management plans were either peak flow or symptom based, which were compared against each other or compared to no written management plan. Reported outcomes included: hospitalisation, emergency department visits, oral corticosteroid use, lung function, days lost from school/work, unscheduled doctor visits and respiratory tract infections. There was no consistent evidence that written plans produced better patient outcomes than no written plan. For some outcomes, there appeared to an advantage of one type of plan over the other, but there was no consistency - one type of plan was not consistently more effective than another.

REVIEWER'S CONCLUSIONS

The available trials are too small and the results too inconsistent to form any firm conclusions as to the contribution of written self management plans in the known beneficial effects of a comprehensive asthma care programmes.

Continuing the debate about measuring asthma in population studies

The reasons for measuring atopy and airway hyperresponsiveness (AHR) and the methods of validating measurements of asthma in population studies continue to be debated. The debate has centred around standards against which to validate asthma measurements but the absence of a "gold standard" makes the criterion validation of measurements difficult. Questionnaires will always be useful but cannot be validated against a doctor diagnosis because of self-selection and recall biases. In practice, measurements should be selected on the merits of what they measure rather than being regarded as validated or non-validated alternatives. The measurement of AHR is invaluable because it is reliable, not influenced by variations in symptom perception or diagnostic trends, and is closely related to the underlying mechanisms of asthma. The value of AHR lies in its high specificity (rate of true negatives) and low sensitivity (rate of false positives) against asthma symptoms which gives additional information about symptomatic subjects. Atopy is also a useful test and, in quantifying its association with asthma, we should not place any currency on ecological evidence. Atopy is a strong risk factor for asthma in the presence of regionally specific allergens and ecological analyses that ignore these effects are diversionary rather than productive. For preventing asthma, we need to identify the group at greatest risk of developing it, measure the risk factors with precision, and develop interventions that are effective in changing environmental exposures and homogeneous outcomes. This is the only approach that has the potential to lead to significant public health benefits.

Problems and possibilities in understanding the natural history of asthma

In early life, asthma symptoms can occur intermittently or may not be severe enough to limit normal activities, which makes it difficult for the clinician to make reliable predictions and administer therapy with some precision. In the case of pediatric asthma, the identification of children who will experience the development of a clinically important illness that will impair their quality of life can be a complex process. The usual methods for describing this information include the prognostic statistics of sensitivity, specificity, likelihood ratio, and positive predictive value. The sensitivity, specificity, and likelihood ratio of various early markers of asthma have been calculated from several cohort studies. (J Allergy Clin Immunol 2000;106:S144-52.)