Biomedical subjects

G B Marks

Publications and source records attributed to G B Marks.

At least 55 records · Page 3Linked to original sources

PubMed2001

Epidemiology of asthma in children. Who gets asthma and why?

BACKGROUND: Asthma is a common disease in childhood which results in a substantial burden of illness in Australia. This is manifest by distressing symptoms, impact on quality of life and role performance and health service utilisation. OBJECTIVE: This article reviews the current literature on the epidemiology of asthma in children. It particularly focuses on the prevalence, trends in prevalence, risk factors and causes of asthma. The emphasis is on common questions that parents of children with asthma would like answered by their general practitioners. DISCUSSION: We know something about some of the risk factors for asthma and a little about the mechanisms for the development of asthma. Despite the paucity of knowledge about the causes of asthma, some positive steps can be taken to prevent it. Allergic or asthmatic parents, whose children have a high risk of developing asthma, can be advised to avoid smoking during pregnancy and avoid environmental tobacco smoke exposure after the child is born, to undertake house dust mite control strategies, to breastfeed their babies for at least three months and subsequently to provide their child with a nutritious, balanced diet.

Asthma↗

PubMed2000

Use of "preventer" medications and written asthma management plans among adults with asthma in New South Wales. NSW Health Department Asthma Data Working Group.

OBJECTIVES: (1) To measure the extent of use of preventer medications (ie, inhaled corticosteroids or cromones) and possession of written asthma management plans (AMPs) among people with asthma in New South Wales in 1997. (2) To assess factors associated with underuse of preventer medications and AMPs. DESIGN AND SETTING: A cross-sectional survey by computer-assisted telephone interviews of a stratified random sample of the adult population of New South Wales, Australia. PARTICIPANTS: People aged 16 to 54 years with asthma diagnosed by a doctor and causing symptoms or requiring treatment in the preceding year (n = 1,372). RESULTS: Although 55.2% of survey participants had used preventer medications in the preceding year, only 27.8% had used them regularly. Only 34.7% had a written AMP. Preventer medications were judged to be indicated for 54% of the study population, but only 42.5% of this group had used them regularly (43.1% had a written AMP). Younger adults were less likely to use preventer medications regularly, but there was no difference in use of preventer medications by sex, urban/rural residence, or manner of purchasing reliever medications (either on prescription or "over the counter"). Past smokers used preventers more commonly than current smokers, with never smokers having an intermediate prevalence of regular preventer use. Age, sex, urban/rural residence, and manner of purchasing reliever medications were not related to the possession of an AMP. CONCLUSION: Despite the trend towards increased use of preventer medications and written AMPs during the 1990s, undertreated asthma remains a major public health problem in Australia.

Adolescent↗

PubMed2000

Daycare attendance before the age of two protects against atopy in preschool age children.

Early attendance at daycare has been shown to protect against atopy, as defined by a positive skin prick test. One proposed hypothesis for this association is that early exposure to other children protects against atopy by facilitating the spread of infections among children. An alternative hypothesis is that children attending daycare centers have less atopy due to lower levels of exposure to indoor allergens. Our aim was to determine whether attendance at daycare before age 2 years protects against atopy in Australian preschool age children and to test the two alternative hypotheses, as well as a number of potential confounding factors. We conducted a cross-sectional study of children aged 3-5 years living in one humid coastal city (Lismore, n = 286) and one dry, inland city (Wagga Wagga, n = 364) in New South Wales, Australia, in 1995. Atopy was assessed by skin prick tests to six common allergens. Daycare attendance and other possible risk factors for atopy were measured by a parent-completed questionnaire. Children who attended daycare before age 2 years had a reduced risk of atopy at 3-5 years. The greatest effect was seen in children who attended a daycare center (odds ratio (OR), 0.26; 95% CI, 0.14-0.50) rather than family daycare (OR, 0.66; 95% CI, 0.41-1.04). The results of this study do not support either of the proposed hypotheses, nor can the effect be explained by any of the other potential confounders measured. Further work is needed to determine the exposure that is responsible for the protective effect of daycare attendance on atopy.

Age Factors↗

PubMed2000

Thunderstorm-associated asthma in an inland town in south-eastern Australia. Who is at risk?

The aim of the study was to characterize patients at risk of asthma exacerbation during spring thunderstorms and identify potential measures to ameliorate the impact of those events. A case-control study was conducted among patients aged 7-60 yrs, who attended Wagga Hospital (NSW, Australia) for asthma during the period of 1 June 1997 to 31 October 1997. One hundred and eighty-three patients who attended on 30 and 31 October 1997 were the cases and the remaining 121 patients were the controls. Questionnaire data were obtained from 148 (81%) cases and 91 (75%) controls. One hundred and thirty-eight (95%) cases who attended during the thunderstorm gave a history of hayfever prior to the event compared to 66 (74%) controls who attended at other times (odds ratio (OR) 6.01, 95% confidence interval (CI) 2.55-14.15); 111 (96%) cases were allergic to rye grass pollen compared to 47 (64%) controls (OR 23.6, 95% CI 6.6-84.3). Among subjects with a prior diagnosis of asthma (64% cases and 82% controls), controls (56%) were more likely to be taking inhaled steroids at time of the thunderstorm than cases (27%, OR 0.3, 95% CI 0.16-0.57). History of hayfever and allergy to rye grass are strong predictors for asthma exacerbation during thunderstorms in spring. The lower rate of inhaled steroid use in thunderstorm cases suggests that this treatment may be effective in preventing severe attacks during thunderstorms.

Adolescent↗

PubMed2000

The effect of insecticide aerosols on lung function, airway responsiveness and symptoms in asthmatic subjects.

The object of this study was to compare the effect of standard and "low irritant" insecticide aerosols on lung function, airway hyperresponsiveness (AHR) and symptoms in asthmatic subjects. A double blind randomized, crossover study was conducted in 25 asthmatic subjects who reported sensitivity to insecticide aerosols. All subjects were exposed for 30 min, on separate occasions, to two standard insecticide formulations (A and B), one low irritant formulation (C) and a negative control aerosol. Spirometric function and chest, nose and eye symptoms were recorded during, and for 90 min after, the exposure. AHR to methacholine was measured 90 min after the exposure. Compared to the negative control, the maximum fall in forced expiratory volume in one second (FEV1) was slightly greater after standard insecticides (mean differences from control +/-95% confidence interval: aerosol A, 3.3+/-3.6%, p=0.08; aerosol B, 5.1+/-4.7%, p=0.04), AHR was significantly more severe (mean difference from control: aerosol A, 0.35+/-0.29 doubling doses, p=0.028; aerosol B, 0.52+/-0.43 doubling doses, p=0.028), and symptoms were more severe. The low irritant test aerosol (C) did not differ significantly from the negative control with respect to FEV1, AHR or symptoms. It is concluded that some insecticide aerosols trigger symptoms and falls in lung function in some people with asthma. Furthermore, these aerosols may also increase airway hyperresponsiveness, although the mechanism of this effect has not been determined. The low irritant formulation did not appear to have the same effects.

Adult↗

PubMed2000

Optimal asthma control, starting with high doses of inhaled budesonide.

The aim of this study was to determine whether outcomes in poorly controlled asthma can be further improved with a starting dose of inhaled budesonide higher than that recommended in international guidelines. The study had a parallel-group design and included 61 subjects with poorly controlled asthma, randomized to receive 3,200 microg or 1,600 microg budesonide daily by Turbuhaler for 8 weeks (double-blind), then 1,600 microg x day(-1) for 8 weeks (single-blind), followed by 14 months of open-label budesonide dose down-titration using a novel algorithm, with a written asthma crisis plan based on electronic peak expiratory flow monitoring. The primary outcome variable for weeks 1-16 was change in airway hyperresponsiveness (AHR), and, for the open-label phase, mean daily budesonide dose. By week 16, there were large changes from baseline in all outcomes, with no significant differences between the 3,200- and 1,600-microg x day(-1) starting dose groups (AHR increased by 3.2 versus 3.0 doubling doses, p=0.7; morning peak flow increased by 134 versus 127 L x min(-1), p=0.8). Subjects starting with 3,200 microg x day(-1) were 3.8 times more likely to achieve AHR within the normal range, as defined by a provocative dose of histamine causing a 20% fall in forced expiratory volume in one second (PD20) of > or = 3.92 micromol by week 16 (p=0.03) [corrected]. During dose titration, there was no significant difference in mean budesonide dose (1,327 versus 1,325 microg x day(-1), p>0.3). Optimal asthma control was achieved in the majority of subjects (at completion/withdrawal: median symptoms 0.0 days x week(-1), beta2-agonist use 0.2 occasions x day(-1), and PD20 2.4 micromol). In subjects with poorly controlled asthma, a starting dose of 1,600 microg x day(-1) budesonide was sufficient to lead to optimal control in most subjects. The high degree of control achieved, compared with previous studies, warrants further investigation.

Administration, Inhalation↗

PubMed2000

Personal exposure to allergenic pollen and mould spores in inland New South Wales, Australia.

BACKGROUND: In inland NSW, Australia, allergic sensitization to the fungi Alternaria and Cladosporium and to pollen is common and an important risk factor for asthma. OBJECTIVE: We report the results of a series of experiments designed to assess the nature of personal exposure to these airborne allergenic particles. We have tested the effect of exposure conditions and level of activity on measurements of the personal exposure. METHOD: Personal Air Samplers (PAS) and Nasal Air Samplers (NAS) were employed. NAS are fitted just inside the nose and collect inhaled particles by impaction, while the PAS use a pump-operated filter with constant air flow (2 L/min). Thirty-three subjects (adults and children) used both NAS and PAS simultaneously for four one hour periods during which they performed activities or rested, both inside and outside their homes. Samples were analysed by light microscopy. Alternaria spores, Cladosporium spores, grass pollen and nongrass pollen were counted. RESULTS: Both samplers detected substantial variation in exposure between subjects. Between members of the same household, the intrahouse correlation coefficient ranged from < 0 - 0.38. Levels of pollen grains and fungal spores inhaled were higher during periods of activity than during rest, and higher while subjects were outdoors than indoors. During the active outdoor period, the number of Alternaria spores inhaled ranged from 4 to 794 (median 11) spores/hr, Cladosporium from 0 to 396 (median 4) spores/hr, grass pollen from 0 to 81 (median 1) grains/hr and nongrass pollen from 0 to 72 (median 5) grains/hr. CONCLUSION: This is the first study to quantify individual inhaled levels of allergenic fungal spores and pollen under normal domestic circumstances. Exposure can be substantial and highly variable between individuals. The amount of particles inhaled relates both to location of the individual and activity being performed, independent of age group.

Adult↗

PubMed2000

Prehospital management of exacerbations of asthma: relation to patient and disease characteristics.

OBJECTIVE: Admission to hospital due to an exacerbation of asthma may represent a failure of prehospital management to prevent an attack or bring about its remission. We aim to describe the steps taken prior to hospital attendance in patients with asthma and to identify patient or disease characteristics that were associated with failure to take appropriate actions. METHODOLOGY: Patients aged over 15 years who were discharged from hospital or the Emergency Department with a primary diagnosis of asthma completed a questionnaire about the impact of asthma and its management prior to the onset of the recent exacerbation. The impact of asthma on quality of life was measured using our Asthma Quality of Life Questionnaire (AQLQ). RESULTS: Seventy-eight subjects completed the questionnaire including 49 who had been inpatients and 29 who had been discharged from the Emergency Department. They included many subjects with severe asthma: 41% had nocturnal symptoms three or more times per week and 41% had been admitted to hospital with asthma in the 12 months prior to this episode. Their AQLQ scores were high (severe) (mean 4.5+/-2.2). Most subjects described their presenting exacerbation as slow in onset and moderate or severe in intensity. During this exacerbation and prior to hospital attendance, only 27% of subjects had measured their peak expiratory flow rate, 19% had commenced or increased the dose of inhaled steroids, and 22% had commenced oral steroids. These actions were not related to the self-perceived speed of onset of the attack. Patients with lower levels of asthma-related concerns for health and more severe mood disturbance associated with asthma were less likely to take these appropriate self-management steps. CONCLUSIONS: This study shows that the failure of prehospital management to prevent the necessity of hospital attendance in most cases stems from a failure to implement currently recommended actions or treatments for exacerbations. Addressing this problem should result in a reduction in rates of hospitalization for asthma.

Adult↗

PubMed2000

Domestic control of house dust mite allergen in children's beds.

BACKGROUND: House dust mite allergen levels in humid coastal regions of Australia are high, particularly in beds. Because high allergen levels in beds are associated with more severe asthma, reduction of levels may be important for asthma control. OBJECTIVE: We tested the effectiveness of an acaricidal treatment of bedding in combination with occlusive mattress and pillow encasings in reducing allergen levels in children's beds in a community setting. METHODS: A total of 14 beds of children were selected for the active intervention. In each home the bed of a sibling of nearest age was selected as the control. Dust was vacuumed from beds by using a standard protocol, and Der p 1 levels were measured by using ELISA. Adjacent settling dust was collected by using opened Petri dishes. The intervention consisted of encasing mattresses and pillows in occlusive covers and washing all bedding with Acaril, an acaricidal additive. The acaricidal wash was repeated twice in 7 households at 2-month intervals. Control beds were not treated. RESULTS: The mean Der p 1 concentration at baseline was 27.9 microg/g in the active beds and 18.1 microg/g in the control beds. At 4 days after intervention, Der p 1 decreased to 3.2 microg/g and 15.7 microg/g in active and control beds, respectively. The average difference (active minus control) over the first 8-week cycle was 78.5% (P <.0001), and the difference over 3 washing cycles was 125.1% (P <.05). The mean rate of settling Der p 1 adjacent to the actively treated beds decreased from 24.4 ng.m(-2).d(-1) at baseline to 10.0 ng.m(-2).d(-1) after intervention (P <.01). CONCLUSION: A substantial reduction in Der p 1 levels in beds and in airborne dust in a humid region with naturally high house dust mite allergen levels can be achieved and sustained in a community setting with use of occlusive covers and a rigorous washing routine.

Allergens↗

PubMed2000

Lung function growth and its relation to airway hyperresponsiveness and recent wheeze. Results from a longitudinal population study.

To evaluate the association between growth in height and growth in lung function, and to identify the potential temporal relationships between airway hyperresponsiveness (AHR), respiratory symptoms, and lung function growth during adolescence and young adulthood, we analyzed data collected from the Belmont cohort. Among the 718 schoolchildren initially studied at 1982 (aged 8-10 yr), 557 were studied between two times and six times at 2-yr intervals until 1992. Baseline lung function, AHR by histamine inhalation test, and recent wheeze by questionnaires, were measured at each visit. We found that between 17 and 19 yr of age, when growth in height had stopped, growth in FEV(1) was approximately 200 ml/yr in boys and 100 ml/yr in girls. Peak growth velocity of height occurred at age 13 both in boys and in girls, whereas peak growth velocity of FEV(1) occurred at the same age only in girls and 1 yr later in boys. Having AHR and recent wheeze at the previous study time were both associated with lower subsequent growth in FEV(1), but not with subsequent growth in FVC. We conclude that lung function continues to grow after the cessation of height growth and that growth in FEV(1) is reduced in subjects with AHR and/or recent wheeze.

Body Height↗

PubMed2000

Incidence of tuberculosis among a cohort of tuberculin-positive refugees in Australia: reappraising the estimates of risk.

Estimates of the lifetime risk of tuberculosis have varied widely and may not be applicable in all current settings. The aim of this study was to measure the incidence of reactivation of latent tuberculosis in a cohort of 15,489 predominantly Southeast Asian refugees aged 12 yr and over who arrived in Sydney, Australia during the period 1984 to 1994 and who had a clear chest X-ray on arrival. Tuberculin skin test (TST) reaction size and the presence of a BCG scar were recorded at entry. Incident cases of tuberculosis, occurring before June 1998, were identified by record linkage analysis with confirmatory review of case notes. There were 122 cases of tuberculosis over an average 10.3 yr of follow-up (crude annual incidence, 76.2/100,000). There was a linear increase in risk with increasing TST reaction size above 10 mm. The risk, and the relation of risk to TST reaction size, were unrelated to BCG scar status. Among those whose initial TST reaction was >/= 15 mm, the annual incidence rate in the first 3 yr was 213 (95% CI, 150 to 300) per 100,000 person-years and in the subsequent 10 yr the rate averaged 122 (95% CI, 90 to 165) per 100,000 person-years. The observed rates are similar to those estimated in the general population of the United States in the 1950s and 1960s. Further data on the prognosis of tuberculosis and the effects of isoniazid preventive therapy in Southeast Asian migrants to Western countries are required to inform policy and practice for the prevention of tuberculosis in this population.

Adolescent↗

PubMed1999

Clustered randomised trial of an intervention to improve the management of asthma: Greenwich asthma study.

OBJECTIVES: To evaluate the effectiveness of an asthma resource centre in improving treatment and quality of life for asthmatic patients. DESIGN: Community based randomised controlled trial. SETTING: 41 general practices in Greenwich with a practice nurse. SUBJECTS: All registered patients aged 15-50 years. INTERVENTION: Nurse specialists in asthma who educated and supported practice nurses, who in turn educated patients in the management of asthma according to the British Thoracic Society's guidelines. MAIN OUTCOME MEASURES: Quality of life of asthmatic patients, attendance at accident and emergency departments, admissions to local hospitals, and steroid prescribing by general practitioners. RESULTS: Of 24 400 patients randomly selected and surveyed in 1993, 12 238 replied; 1621 were asthmatic of whom 1291 were sent a repeat questionnaire in 1996 and 780 replied. Of 24 400 patients newly surveyed in 1996, 10 783 (1616 asthmatic) replied. No evidence was found for an improvement in asthma related quality of life among newly surveyed patients in intervention practices compared with control practices. Neither was there evidence of an improvement in other measures of the quality of asthma care. Weak evidence was found for an improvement in quality of life in intervention practices among asthmatics registered with study practices in 1993 and followed up in 1996. Neither attendances at accident and emergency departments nor admissions for asthma showed any tendency to diverge in intervention and control practices over the study period. Steroid prescribing rates rose steadily during the study period. The average annual increase in steroid prescribing was 3% per year higher in intervention than control practices (95% confidence interval -1% to 6%, P=0.10). CONCLUSIONS: This model of service delivery is not effective in improving the outcome of asthma in the community. Further development is required if cost effective management of asthma is to be introduced.

Adolescent↗

PubMed1999

Specificity of notification for tuberculosis among screened refugees in NSW.

OBJECTIVE: Epidemiological surveillance of tuberculosis (TB) in Australia is dependent on the accuracy of the notification data. We have investigated the specificity of TB notification for the diagnosis of this disease. METHOD: We used data from notifications to the NSW Department of Health to identify members of a cohort of refugees who were screened between 1984 and 1993 and subsequently developed TB during that period. We reviewed notification data and, in most instances, case notes and x-ray films, to independently confirm or refute the diagnosis of TB. RESULTS: Two hundred and fifty members of the cohort were identified in the notification database. After excluding refugees on treatment prior to arrival in Australia, and those who were notified as 'quiescent' and 'atypical' cases, there were 189 cases notified as active TB. There was evidence to support the diagnosis of active TB in 125 cases (66%) and evidence that subjects did not have active disease in 60 cases (32%). We could not determine the status of the remaining four notified cases. CONCLUSION: This study has shown that, in a population of refugees subject to screening, nearly one-third of cases notified as active tuberculosis from the study population were actually not active tuberculosis cases. IMPLICATIONS: The use of the TB notification database may result in overestimation of the incidence of TB in population groups who are subject to active screening.

Bias↗

PubMed1999

Exhaled nitric oxide measurements in a population sample of young adults.

In epidemiologic studies of asthma there is a group with recent wheeze, but with no airway hyperresponsiveness (AHR), in whom it is unclear whether any significant airway abnormality exists. Exhaled nitric oxide (NO) has been proposed as a measure of airway inflammation. We measured exhaled NO in a population sample of 306 young adults who also underwent bronchial challenge with histamine or a bronchodilator test. Subjects blew into a 3-L Tedlar bag against a 2-mm-diameter resistance to close the soft palate and exclude nasal air. The NO content of expired gas from a single breath was analyzed by chemiluminescent analyzer. Exhaled NO was log-normally distributed in the population sample and duplicate measurements were highly reproducible (intraclass correlation coefficient = 0.98). Exhaled NO correlated significantly with airway responsiveness, measured as the dose-response ratio to histamine (r = 0.39, p < 0.001) and with peripheral blood eosinophils (r = 0.35, p < 0.001). Exhaled NO was significantly greater in asthmatic subjects (geometric mean, 22.2; 95% confidence intervals, 16.1 to 30. 7 ppb) than in normal subjects (7.8, 7.1 to 8.4, p < 0.001) or in subjects with wheeze but no AHR (8.8, 7.5 to 10.3, p < 0.001). We conclude that exhaled NO is log-normally distributed, is highly reproducible and discriminates well among subjects, suggesting that it is both a feasible and useful measurement for epidemiologic studies of asthma. The findings suggest that wheeze in the absence of AHR is unlikely to be associated with airway inflammation.

Adult↗

PubMed1999

The message from the World Asthma Meeting. The Working Groups of the World Asthma Meeting, held in Barcelona, Spain, December 9-13, 1998.

The 1998 World Asthma Meeting (WAM) has been the first multidisciplinary event aimed to consider asthma as a global public health problem in children and adults. The purpose of the meeting was to present state-of-the-art scientific information and to make recommendations on the research agenda for the coming years. Five Working Groups of invited experts were appointed to pin-point the established knowledge and the important questions in the areas of epidemiology, prevention, pathogenesis, management, and education. Their reports were discussed during the final plenary session, and are forming the current proceedings of the meeting. The message of the World Asthma Meeting provides a research agenda supported by the major international bodies involved in this disease. An integrated approach is considered to be essential in order to improve the prevention and care of asthma in all countries of the world.

Adult↗

PubMed1998

Serum eosinophil cationic protein: distribution and reproducibility in a randomly selected sample of men living in rural Norfolk, UK.

BACKGROUND: It has been proposed that serum levels of eosinophil cationic protein (ECP) may be a clinically useful measure in allergic illness. The aim of this report is to describe the distribution and reproducibility of serum ECP levels in a population sample and to examine its relationship with other markers of disease. METHODS: The study was conducted in rural areas of Norfolk, UK in a random sample of men aged 20-44 years enriched with subjects drawn from general practice 'asthma registers'. Asthma symptoms were assessed using the EC Respiratory Health Survey questionnaire. Atopy was measured by skin prick tests and serum IgE. Airway hyperresponsiveness (AHR) was tested by methacholine challenge test. Serum IgE and ECP was measured by fluoroimmunoassay using the Pharmacia CAP system. Reference equations were derived in subjects from the random sample who did not have symptoms of asthma, abnormal lung function or AHR. The relation of serum ECP with various clinical characteristics was examined in the whole study population. Reproducibility of serum ECP measurement was assessed in 57 subjects 4 weeks after the initial test. RESULTS: The study population comprised 311 from the random sample and 58 from the asthma sample. The reference equation for serum ECP for healthy men was log10 ECP = 1.3966 - [(age - 20) x 0.0057]. The estimated mean serum ECP for a 20-year-old man was 25 microg/L. Current smokers have higher serum ECP levels that non-smokers (P = 0.014). ECP levels were not related to the skin prick test reactivity, serum IgE, a questionnaire-based diagnosis of asthma, or impaired lung function (all P > 0.05). Levels were higher in subjects with AHR (P = 0.003) and those who reported wheeze (P = 0.017) but there was no clinically useful separation in ECP levels between subjects classified by these criteria. The test was moderately reproducible over a 4-week period (intraclass correlation coefficient = 0.62). DISCUSSION: Serum ECP levels were higher in this rural English population than reported in a comparable population in Sweden. Serum ECP is a reproducible test but cross-sectionally does not relate in any clinically useful way to markers of asthma. The meaning of between- subject differences in ECP levels requires further exploration.

Adult↗

PubMed1998

House dust mite exposure as a risk factor for asthma: benefits of avoidance.

There is a dose-response relation between the level of exposure to house dust mite allergen and the risk of acquiring sensitization to this allergen as well as the risk of developing asthma. This relation is apparent at levels of exposure below 10 microg/g. In communities where nearly all houses have house dust mite allergen levels above this threshold, all susceptible individuals will be affected, and the relation to house dust mite exposure will not be apparent. Although these observational data would suggest that reducing exposure to house dust mite allergen should lessen the risk of developing sensitization and asthma, definitive evidence from randomized controlled trials is not yet available. Of the many clinical trials of house dust mite avoidance as therapy for asthma, only a few have produced sustained, substantial reductions in allergen levels in the bed. These effective interventions all included allergen-impermeable encasement of mattresses along with other strategies. In most trials where allergens levels were successfully reduced, there were clinical benefits for patients with asthma.

Allergens↗

PubMed1998

Standardization of ambulatory peak flow monitoring: the importance of recent beta2-agonist inhalation.

Standardization of conditions for peak expiratory flow (PEF) monitoring is much more difficult in practice than for laboratory spirometry. Patients are usually asked to record PEF before medication. The aim of this study was to determine the effect of prior bronchodilator use on PEF outcome measures in a clinical trial. Electronic PEF records from 43 subjects with poorly controlled asthma were examined to determine the frequency with which beta2-agonist was inhaled <4 h before PEF measurement, as such PEF are potentially "postbronchodilator". The effect of inclusion of such PEF values on improvement in PEF outcome measures after 8 weeks of inhaled budesonide was calculated. Subjects were asked to record PEF before medication. During run-in, the median frequency of postbronchodilator PEF was 29%, falling to 0% after 8 weeks of budesonide. Inclusion of postbronchodilator PEF led to an overestimation of average morning, evening and daily PEF during run-in (p<0.001). Improvement in these indices with treatment was, therefore, underestimated. Minimum morning PEF expressed as per cent personal best was unaffected. Subjects may not be able to withhold beta2-agonist for 4 h before every peak flow reading. This may change as the level of asthma control changes, leading to a systematic bias in clinical trial end-points or inaccuracy in individual treatment decisions. Simple changes to peak expiratory flow instructions and analysis are proposed.

Administration, Inhalation↗