Risk of severe life threatening asthma and beta agonist type: an example of confounding by severity

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

Asthma and delirium episodes during hospitalization

BACKGROUND

Delirium incidences during hospitalization are an important problem in elderly patients. The problem of delirium episodes in patients with obstructive disease during hospitalization was investigated.

MATERIAL AND METHODS

From a total of 37,156 subjects, the following were randomly selected: 32,261 patients with asthma, 4896 with chronic obstructive pulmonary disease (COPD), and 5455 without obstructive disease. Their ages ranged from 65-95 years, and they were hospitalized between 2006 and 2015. Delirium incidences were monitored based on the International Classification of Disease (ICD)-10 codes and medical documentation.

RESULTS

The delirium episodes during all hospitalizations were independently associated with asthma (odds ratio [OR] = 2.91, confidence interval [CI] = 1.62-5.84), with severe type of asthma (OR = 4.24, CI = 1.94-8.93), partim controlled asthma (OR = 3.1, CI = 1.29-8.46), and uncontrolled asthma (OR = 4.88, CI = 2.12-9.42). It was comparable with COPD as follows: all incidences of delirium during hospitalization (OR = 3.17, CI = 1.42-7.23) or severe COPD (III degree OR = 5.15, CI = 2.01-13.69). Elderly patients with asthma with uncontrolled or partially controlled asthma with a coincidence of advanced age, dementia, or smoking had a greater predisposition to delirium episodes, particularly after surgery. Additionally, delirium incidence caused death more frequently in patients with asthma than in those with COPD.

CONCLUSION

Elderly patients with asthma have a higher risk of delirium episodes during any hospitalization, and, frequently, it ends in death.

The importance and implications of comparator selection in pharmacoepidemiologic research

PURPOSE OF REVIEW

Pharmacoepidemiologic studies employing large databases are critical to evaluating the effectiveness and safety of drug exposures in large and diverse populations. Because treatment is not randomized, researchers must select a relevant comparison group for the treatment of interest. The comparator group can consist of individuals initiating: (1) a similarly indicated treatment (active comparator), (2) a treatment used for a different indication (inactive comparator) or (3) no particular treatment (non-initiators). Herein we review recent literature and describe considerations and implications of comparator selection in pharmacoepidemiologic studies.

RECENT FINDINGS

Comparator selection depends on the scientific question and feasibility constraints. Because pharmacoepidemiologic studies rely on the choice to initiate or not initiate a specific treatment, rather than randomization, they are at-risk for confounding related to the comparator choice including: by indication, disease severity and frailty. We describe forms of confounding specific to pharmacoepidemiologic studies and discuss each comparator along with informative examples and a case study. We provide commentary on potential issues relevant to comparator selection in each study, highlighting the importance of understanding the population in whom the treatment is given and how patient characteristics are associated with the outcome.

SUMMARY

Advanced statistical techniques may be insufficient for reducing confounding in observational studies. Evaluating the extent to which comparator selection may mitigate or induce systematic bias is a critical component of pharmacoepidemiologic studies.

Beta2-adrenergic agonist use and the risk of multiple sclerosis: a total population-based case-control study

OBJECTIVE

The aim of this study was to investigate whether the use of fenoterol, a beta2-adrenergic agonist, was associated with multiple sclerosis (MS) risk by conducting a total population-based case-control study in Taiwan.

METHODS

A total of 578 patients with newly diagnosed MS who had a severely disabling disease (SDD) certificate between January 1, 2002 and December 1, 2008 comprised the case group. These cases were compared with 2890 gender-, age-, residence-, and insurance premium-matched controls. Fenoterol use was analyzed using a conditional logistic regression model that controlled for asthma, chronic obstructive pulmonary disease (COPD), salbutamol and steroid use.

RESULTS

Compared with the group of people who did not use fenoterol, the adjusted odds ratios were 0.67 (95% confidence interval (CI) = 0.48-0.93, p = 0.016) for the group prescribed fenoterol below 2.25 cumulative defined daily dose (cDDD) and 0.49 (95% CI = 0.33-0.71, p < 0.001) for the group with a cumulative fenoterol use of more than 2.25 cDDD. The dose-response relationship was similar within the non-asthma patients. The associations were similar between males and females, but differences between age groups were observed.

CONCLUSIONS

The results of this study suggest that fenoterol use may reduce the risk of MS.

Continuity of prescribers of short-acting beta agonists among children with asthma

OBJECTIVE

To determine whether short-acting beta-agonist (SABA) prescriber continuity was associated with emergency department visits among children with asthma.

STUDY DESIGN

An analysis of Michigan Medicaid administrative claims (2004-2005) for children ages 5 to 18 with asthma. Logistic regression models assessed the effect of SABA prescriber continuity (the number and site of prescribers) on emergency department visits, controlling for demographics, historical (2004) asthma use and SABA prescription frequency (2-5 low; > or = 6 high).

RESULTS

Most children had one SABA prescriber (62%); 13% had multiple prescribers in the same practice as the primary care provider and 25% had multiple prescribers in different practices. Children with multiple prescribers in different practices had increased odds of an emergency department visit compared with those with 1 prescriber, among those with high SABA prescription frequency (AOR: 2.7, 95% CI: 1.9, 3.9), as well as those with low prescription frequency (AOR: 1.7, 95% CI: 1.3, 2.2).

CONCLUSIONS

Children with discontinuity of SABA prescribers have an increased risk of asthma emergency department visits, irrespective of their SABA prescription frequency. Primary care providers may have difficulty identifying patients at high risk with asthma solely on the basis of SABAs prescribed within their own practices.

Antidepressant adequacy and work status among medicaid enrollees with disabilities: a restriction-based, propensity score-adjusted analysis

Abstract This cross-sectional study of adult survey respondents with disability and depression (n = 199) enrolled in Massachusetts' Medicaid program examined the association of adequately or inadequately prescribed antidepressant treatment and self-reported work status using conditional logistic regression, controlling for age, gender, race, marital status, education, receipt of SSI/SSDI, self-reported disabling condition, and health status. Confounding by severity was addressed by two methods: restriction of our sample and subsequent stratification by propensity score. Individuals receiving adequate antidepressant treatment had an increased odds of working compared to individuals receiving inadequate treatment, both in analyses in which restriction was used to limit confounding (OR = 3.45, 95% CI = 1.15-10.32, P < .03), and in analyses which combined restriction with adjustment by propensity score stratification (OR = 3.04, 95% CI = 1.01-9.62, P < .05). Among this sample of Medicaid enrollees with disability and depression, those receiving adequate antidepressant treatment were significantly more likely to report working.

Pharmacogenetics of asthma

Asthma is a common disease characterized by airway inflammation and bronchorestriction. There are several common categories of medications for treating asthma; however, not all asthmatics have the same response to these medications, some of which are adverse responses that are potentially life threatening. Because interindividual responses to asthma medications can vary considerably, the potential for genetic contributions to variable drug responses is significant. This chapter reviews the most common biological pathways targeted by asthma therapy and briefly discusses the genetic contribution to varied responses to asthma therapy for four common types of asthma medications: beta-agonists, anticholinergics, leukotriene modifiers, and corticosteroids.

Serious adverse events and death associated with treatment using long-acting beta-agonists

Two very large, randomized, double-blind clinical trials performed in the United Kingdom and in the United States have suggested that addition of salmeteräE to usual asthma therapy is associated with a significant increase in the incidence of serious adverse events and asthma-related deaths compared with addition of albuterol or placebo to usual therapy in the same type of patients. These results prompted the United States Food and Drug Administration (FDA) to issue a stern warning regarding these potential adverse effects and to advise that long-acting beta-agonists (LABAs) should not used as first-line therapy for the treatment of asthma. Two potential explanations have been proposed for these unexpected adverse effects. It has been suggested that more than a direct pharmacological effect of LABAs, these adverse events result from inadequate concomitant use of inhaled corticosteroids in subjects treated with these medicines. However, a detailed analysis of the results of the two large trials did not provide definitive conclusions regarding the potential protective role of inhaled corticosteroids. A second explanation, which the author here considers more plausible, is that a small group of patients with asthma develop idiosyncratic responses to LABAs, and common or rare variants in the genes that encode for proteins associated with the pharmacological response to these medicines are strongly suspected to predispose for these unusual deleterious responses. Until the biological mechanisms involved are better understood, efforts should be made to confine the use of LABAs to those patients who really need them.

A systematic review of the psychological risk factors associated with near fatal asthma or fatal asthma

Psychological factors such as anxiety, depressive disorders and/or personality disorders may predispose patients with asthma to near fatal asthma (NFA) or fatal asthma (FA). NFA is defined by an asthma exacerbation resulting in respiratory arrest requiring mechanical ventilation or a pCO(2) >or=45 mm Hg. Most studies have used the case-control study design. Several studies analyzing the effects of psychological factors on the risk of NFA or FA have shown conflicting results. We reviewed all of the literature found by the systematic search done of psychological factors on the risk NFA or FA. A MEDLINE search identified 423 articles between 1960 and March 2006. Seven case-controlled studies were identified following strict applications of the inclusion and exclusion criteria. Due to the significant heterogeneity in the measurement of the psychological factors, a summary statistic was not calculated. The trial characteristics were tabulated and qualitative trends were observed to explain the heterogeneity in the results of the studies. Recommendations on future studies in the field are outlined in detail. Following a systematic assessment of all published studies, we cannot conclude that psychological factors increase the risk of NFA and FA.

[The therapeutic index in asthma: how should it be defined?]

INTRODUCTION

The therapeutic index (efficacy/tolerance or benefit/risk ratio) is a major determinant of treatment decisions in asthma.

METHODS

For the numerator, the therapeutic index depends on efficacy (maximal effect) and not potency (dose-response relationship). With regard to the denominator, several pharmacological factors influence the occurrence of side-effects, the acceptability of which also has to be considered.

RESULTS

In asthma, some strategies have a more favourable therapeutic index than others;e.g additional treatment (long acting beta2 agonists, leukotriene receptor antagonists, theophylline) to inhaled corticosteroids instead of doubling the dose of the latter. Conversely, it is extremely difficult to compare the therapeutic indices of different molecules of inhaled corticosteroids.

CONCLUSIONS

The potential risk of systemic side effects with long-term administration of high doses of inhaled corticosteroids suggests the need to seek the minimal effective dose.

Adverse effects of beta-agonists: are they clinically relevant?

Inhaled beta(2)-adrenoceptor agonists (beta(2)-agonists) are the most commonly used asthma medications in many Western countries. Minor adverse effects such as palpitations, tremor, headache and metabolic effects are predictable and dose related. Time series studies suggested an association between the relatively nonselective beta-agonist fenoterol and asthma deaths. Three case-control studies confirmed that among patients prescribed fenoterol, the risk of death was significantly elevated even after controlling for the severity of asthma. The Saskatchewan study not only found an increased risk of death among patients dispensed fenoterol, but also suggested this might be a class effect of beta(2)-agonists. However, in subsequent studies, the long-acting beta(2)-agonist salmeterol was not associated with increased asthma mortality. In a case-control study blood albuterol (salbutamol) concentrations were found to be 2.5 times higher among patients who died of asthma compared with controls. It is speculated that such toxic concentrations could cause tachyarrhythmias under conditions of hypoxia and hypokalemia. The risk of asthma exacerbations and near-fatal attacks may also be increased among patients dispensed fenoterol, but this association may be largely due to confounding by severity. Although salmeterol does not appear to increase the risk of near-fatal attacks, there is a consistent association with the use of nebulized beta(2)-agonists. Nebulized and oral beta(2)-agonists are also associated with an increased risk of cardiovascular death, ischemic heart disease and cardiac failure. Caution should be exercised when first prescribing a beta-agonist for patients with cardiovascular disease. A potential mechanism for adverse effects with regular use of beta(2)-agonists is tachyphylaxis. Tachyphylaxis to the bronchodilator effects of long-acting beta(2)-agonists can occur, but has been consistently demonstrated only for formoterol (eformoterol) a full agonist, rather than salmeterol, a partial agonist. Tachyphylaxis to protection against induced bronchospasm occurs with both full and partial beta(2)-agonists, and probably within a matter of days at most. Underlying airway responsiveness to directly acting bronchoconstricting agents is not increased when the bronchodilator effect of the regular beta(2)-agonist has been allowed to wear off, although there may be an increase in responsiveness to indirectly acting agents. While there has been speculation that underlying airway inflammation in asthma may be made worse by regular use of short-acting beta(2)-agonists, in contradistinction, a number of studies have shown that long-acting beta(2)-agonists have positive anti-inflammatory effects. An Australian Cochrane Airways Group systematic review of the randomized, controlled trials of short-acting beta-agonists found only minimal and clinically unimportant differences between regular use and use as needed. Regular short-acting treatment was better than placebo. However, a subsequent systematic review has found that regular use of long-acting beta-agonists had significant advantages over regular use of short-acting beta-agonists. More studies and data are needed on the regular use of beta(2)-agonists in patients not taking inhaled corticosteroids, and in potentially vulnerable groups, such as the elderly and those with particular genotypes for the beta-receptor, who might be more prone to adverse effects.

Food allergy as a risk factor for life-threatening asthma in childhood: a case-controlled study

BACKGROUND

No objective clinical risk factors exist for pediatric life-threatening asthma.

OBJECTIVES

In this study, we address whether persistent food allergy and degree of atopy are risk factors for life-threatening asthma.

METHODS

By use of a case-controlled design, children (1-16 years) ventilated for an exacerbation of asthma were enrolled. Each case was matched by sex, age, and ethnicity, with 2 controls who had attended with a non-life-threatening exacerbation. All subjects were assessed by means of a questionnaire, spirometry, and skin prick or RAST testing. The data were analyzed by conditional logistic regression.

RESULTS

Nineteen cases and 38 controls were enrolled. Compared with controls, cases were found to have the following risk factors: food allergy (odds ratio, 8.58; 95% CI, 1.85-39.71), multiple allergic diagnoses (4.42; 1.17-16.71), early onset of asthma (6.48; 1.36-30.85), and frequent admissions (14.2; 1.77-113.59). After regression analysis, only frequent admission with asthma (9.85; 1.04-93.27) and food allergy (5.89; 1.06-32.61) were independently associated with life-threatening asthma. Half the cases had food allergy compared with only 10% of controls.

CONCLUSION

This study demonstrates that poorly controlled asthma and food allergy are significant risk factors for life-threatening asthma. More intensive management of this high-risk group of children might help to reduce future morbidity and mortality.

Is there any association between inhaled ipratropium and mortality in patients with COPD and asthma?

BACKGROUND

To determine whether ipratropium was associated with premature death in patients with asthma and chronic obstructive pulmonary disease (COPD).

METHODS

A longitudinal cohort of 827 patients with COPD and 273 with asthma who were evaluated for compensation by two specialists in pulmonary medicine.

RESULTS

By June 1999, 538 of the patients with COPD and 77 of those with asthma had died. Atthe consultation, 77% ofthe COPD patients and 8.1% of the asthmatic patients were treated with inhaled ipratropium. Ipratropium was associated with mortality risk ratio (RR) of 2.0 (95% confidence interval: 1.5-2.6) for COPD and 3.6 (1.8-7.1) for asthma patients. After adjustment for confounding factors [forced expiratory volume 1 s (FEV1), smoking habits, asthma medication, and presence of cor pulmonale] the RR for COPD was 1.6 (1.2-2.1) and for asthma 24 (1.2-5.0).

CONCLUSIONS

The increased risk of premature death associated with ipratropium is of concern and necessitates further evaluation, e.g., in a randomised study.

A case-control study of asthma death and life-threatening attack: their possible relationship with prescribed drug therapy in Japan

Sales of inhaled beta2-agonist bronchodilators may be related to the increase in asthma deaths. The aim of this study is to find whether prescribed drug therapy was associated with the increased risk of death from asthma and life-threatening attacks (LTA). The "case" group comprised those under 35 years of age who expired or experienced LTA from January 1994 through December 1996. For each case, an age and sex matched control was selected from asthma patients. Hospital records were reviewed to obtain information on the prescribed drug therapy and clinical asthma severity for the cases and controls. Bivariate analysis with conditional logistic regression models for matched data sets were used to estimate the severity-adjusted odds ratios for each asthma medication. Twenty-four fatal cases and 54 LTA cases were observed. The crude odds ratio of clinical severity (OR=9.33, 95%CI:2.84-30.7) was larger than unity and with statistical significance. After adjusting for clinical severity, the odds ratios computed for all beta2-agonists delivered by metered dose inhaler (MDI) increased (OR=2.08, 95%CI:0.78-5.50) from that of crude analysis. Among those subjects under 20 years of age, the clinical severity-adjusted odds ratio for the use of all beta2-agonists by MDI (OR=3.67, 95%CI:0.77-17.5) was higher than that of all subjects. The prescription of B2-agonists by MDI increased the risk of asthma death after taking clinical severity into account. Although not statistically significant, our results suggested that beta2-agonists administered by a MDI might have increased the risk of asthma death and LTA in Japan because the magnitude of the effect was similar to that reported in other countries.

Case-control study of severe life threatening asthma (SLTA) in adults: psychological factors

BACKGROUND

Severe life threatening asthma (SLTA) is important in its own right and as a proxy for asthma death. In order to target hospital based intervention strategies to those most likely to benefit, risk factors for SLTA among those admitted to hospital need to be identified. Adverse psychological factors are purported risk factors for asthma death and SLTA /near fatal asthma. A study was undertaken to determine whether, in comparison with patients admitted to hospital with acute asthma, those with SLTA have specific adverse psychological factors.

METHODS

A case-control study was undertaken. Cases (n=77) were admitted to the intensive care unit with SLTA (mean (SD) pH 7.17 (0.15), PaCO(2) 10.7 (5.0) kPa). Controls (n=239) were admitted to general wards with acute asthma and were matched only by date of index attack. An interviewer administered questionnaire was undertaken 24-48 hours after admission. A random sample of community based asthmatics was recruited to provide normative data on asthmatics for comparison with cases and hospital controls.

RESULTS

The risk of SLTA increased with age (OR 1.04/year, 95% CI 1.01 to 1.07) and was less for women (OR 0.36, 95% CI 0.20 to 0.68). These variables were controlled for in all further analyses. There was a high prevalence of psychological disorder in both cases and matched controls, but there was no difference in prevalence of caseness for anxiety or depression, total (or individual) life events in last 12 months, availability of general or disease specific social support, nor in any of the domains of the Attitudes and Beliefs about Asthma Questionnaire (emotional (mal) adjustment, doctor-patient relationship, stigma, self-efficacy). Cases (SLTA) were less likely to have had previous emotional counselling (25% v. 35%, p<0.05). However, when comparison was made with a community based group of asthmatic patients, those admitted to hospital with acute asthma (SLTA and hospital controls) had a higher prevalence of anxiety and depression, higher total life events, and higher prevalence of certain specific life events.

CONCLUSIONS

There was considerable psychological morbidity generally (and anxiety specifically) in those admitted with acute asthma. Specific adverse psychological factors were not risk factors for SLTA, when comparison was made with those admitted to hospital with acute asthma, but adverse psychological factors were a risk factor for hospitalisation for acute asthma (including SLTA). Psychological risk factors for adverse events in asthma are dependent both on the type of event under study and the comparison group used.

Cardiovascular side effects of inhaled salbutamol in hypoxic asthmatic patients

BACKGROUND

Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and beta2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the effect of hypoxia on the systemic vascular effects of salbutamol in patients with asthma who are hypoxic by assessing forearm blood flow (FBF) as a measure of peripheral vasodilatation.

METHODS

Eight men with mild asthma underwent the following treatments: normoxia + placebo (NP), normoxia + salbutamol (NS), hypoxia + placebo (HP), and hypoxia + salbutamol (HS). The period of mask breathing started at t=0 minutes, lasted for 60 minutes, and at 30 minutes 800 microg salbutamol was inhaled. The experiment was completed 30 minutes after the inhalation (t=60 minutes). For the hypoxia treatment the SpO2 level was 82%. Differences between treatments were sought using factorial ANOVA on percentage change from the pretreatment value.

RESULTS

There were no significant differences in blood pressure and potassium levels between the treatments. After 60 minutes the increase in FBF was 13% (95% CI -12 to 39) more for HP treatment than for NP, 21% (95% CI -5 to 46) more for NS than for NP, and 32% (95% CI 7 to 58) more for HS than for HP (p=0.016). The inhalation of salbutamol during hypoxia resulted in a significant increase in FBF of 45% (95% CI 20 to 71) compared with NP (p=0.001).

CONCLUSION

Patients with asthma who are hypoxic and inhale beta2 agonists have serious systemic vascular side effects which may be an additional explanation for the association between asthma treatment and sudden death.

Cardiovascular side effects of inhaled salbutamol in hypoxic asthmatic patients

BACKGROUND

Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and β2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the effect of hypoxia on the systemic vascular effects of salbutamol in patients with asthma who are hypoxic by assessing forearm blood flow (FBF) as a measure of peripheral vasodilatation.

METHODS

Eight men with mild asthma underwent the following treatments: normoxia + placebo (NP), normoxia + salbutamol (NS), hypoxia + placebo (HP), and hypoxia + salbutamol (HS). The period of mask breathing started at t=0 minutes, lasted for 60 minutes, and at 30 minutes 800 μg salbutamol was inhaled. The experiment was completed 30 minutes after the inhalation (t=60 minutes). For the hypoxia treatment the Spo2 level was 82%. Differences between treatments were sought using factorial ANOVA on percentage change from the pretreatment value.

RESULTS

There were no significant differences in blood pressure and potassium levels between the treatments. After 60 minutes the increase in FBF was 13% (95% CI –12 to 39) more for HP treatment than for NP, 21% (95% CI –5 to 46) more for NS than for NP, and 32% (95% CI 7 to 58) more for HS than for HP (p=0.016). The inhalation of salbutamol during hypoxia resulted in a significant increase in FBF of 45% (95% CI 20 to 71) compared with NP (p=0.001).

CONCLUSION

Patients with asthma who are hypoxic and inhale β2 agonists have serious systemic vascular side effects which may be an additional explanation for the association between asthma treatment and sudden death.

Prevalence of asthma among schoolchildren in Patras, Greece: three surveys over 20 years

BACKGROUND

The aim of the present study was to compare the prevalence of asthma among schoolchildren in 1978, 1991, and 1998 in Patras, Greece.

METHODS

The study populations of the three comparable cross sectional surveys comprised third and fourth grade public school children in Patras, Greece. Sample sizes in 1978, 1991, and 1998 were 3735, 2952 and 3397 children and response rates were 80.4%, 81.9%, and 90.6%, respectively. Prevalence of current, non-current, and lifetime asthma or recurrent wheezing was determined by parental questionnaire. Personal communication with the parents of asthmatic children in 1991 and 1998 provided data on lost schooldays.

RESULTS

Prevalence rates of current asthma or wheezing in 1978, 1991, and 1998 were 1.5%, 4.6%, and 6.0%, respectively (1978-91: p=0.01, 1991-98: p=0.02, 1978-98: p=0.03). Lifetime prevalences of asthma or wheezing in 1991 and 1998 were 8.0% and 9.6%, respectively (p=0.03). Current diagnosed asthma increased proportionally to diagnosed wheezing during 1991-98. The number of schooldays lost in the previous 2 years because of asthma did not change (p>0.1) between 1991 (0.31 per child) and 1998 (0.34 per child).

CONCLUSIONS

Our results support a true increase in the prevalence of current and lifetime asthma in the last 20 years among pre-adolescent children in Patras, Greece.

Acute asthma

OBJECTIVE: Asthma is the most common medical emergency in children. It is associated with significant morbidity and mortality rates and poses a tremendous societal burden worldwide. Management of the acute attack involves a stepwise approach that includes beta-agonist and steroid therapy, the mainstay of emergency treatment. Most patients will respond to this regime and can be discharged from the emergency department. Failure to respond to treatment necessitates hospital admission and sometimes admission to the intensive care unit (ICU). Management in the ICU involves intensification of pharmacologic therapy, including nonstandard therapies, in an attempt to avoid intubation and ventilation. When needed, mechanical ventilatory support can be rendered fairly safe with little morbidity if the likely cardiorespiratory physiologic derangements are appreciated and if appropriate ventilatory strategies are used. In the past two decades, the availability of newer potent medications and changes in approach to monitoring and ventilatory strategies have resulted in a decrease in ICU morbidity and mortality rates. Research endeavors are presently underway to further characterize the underlying mechanisms of the disease and are likely to lead to novel therapies. This article reviews the approach to management of acute severe asthma.

Beta agonists, inhaled steroids, and the risk of intensive care unit admission for asthma

Although inhaled corticosteroid (ICS) use is associated with a decreased risk of hospitalization for asthma, the impact of ICS on the risk of life-threatening asthma exacerbation is less clear. The effect of ICS and inhaled beta agonist (IBA) dispensing on the risk of intensive care unit admission for asthma, a surrogate for life-threatening exacerbation, is evaluated. Using computerized International classification of diseases (ICD)-9 discharge diagnoses, a cohort of all 2,344 adult Northern California members of a health maintenance organization hospitalized for asthma over a 2-yr period were identified. Computerized pharmacy data was used to ascertain asthma medications dispensed during the 3-,6-, and 12-month intervals preceding index hospitalization for asthma. During the 3-months preceding hospitalization, a minority of subjects had no IBA units dispensed (34%), with 14% receiving low level (1 unit), 20% medium level (2-3 units), and 32% high level (> or = 4 units) therapy. A substantial proportion received no ICS units (55%), whereas 13% had low, 16% medium, and 15% high level therapy. In multiple logistic regression analysis, high level IBA use was associated with a greater risk of intensive care unit (ICU) admission for asthma after controlling for asthma severity. There was no relationship, however, between low or medium level IBA use and ICU admission. Conversely, medium level and high level ICS use were associated with a reduced risk of ICU admission. Analysing 6- and 12-month medication dispensing data, similar risk patterns were observed. Inhaled corticosteroid dispensing was associated with reduced risk of intensive care unit admission among adults hospitalized for asthma, whereas the opposite applied for high dose beta agonist usage. This suggests that ICS prescription to adults with moderate-to-severe asthma could reduce the risk of life-threatening exacerbation.

Clinical characteristics of asthmatic patients prescribed various beta-agonist metered-dose inhalers at Yamagata University Hospital

To determine the prescription characteristics of beta-agonist metered-dose inhalers (MDI), we retrospectively investigated all prescriptions containing one of five types of beta-agonist MDIs available at Yamagata University Hospital in 1997, as well as patients' characteristics. The total number of asthmatic patients was 225 (age, 11-79, mean, 47.2) in 1997. Fenoterol MDI was prescribed to patients who visited the hospital at regular periods and had more severe asthma. Isoprenaline MDI also was not prescribed for first-time patients. Patients who were prescribed tulobuterol MDI had mild or moderate asthma and some of them were only occasional or first-time visitors. Salbutamol and procaterol MDIs were also prescribed for first-time patients; however, tulobuterol MDI was the most frequently prescribed for first-time patients. Patients prescribed fenoterol and isoprenaline MDIs had adequate knowledge of proper asthma management, because sufficient information had been provided about the use of MDIs in the past. Patients prescribed tulobuterol MDI should be provided with detailed instructions because they had little knowledge of handling MDIs and self-management of asthma as many of them were first or intermittent visitors. Patients prescribed salbutamol or procaterol MDIs should be evaluated regarding their past medications and some of them should be instructed regarding the use of the MDI. Although these clinical aspects might be applicable only to our hospital, the same or other prescription patterns will be found in other hospitals and/or by other physicians. Adequate instructions to individual patients who are prescribed a particular beta-agonist MDI should be provided by the medical staff, especially to outpatients, to reduce hospitalization and death from asthma.

Are asthma medications and management related to deaths from asthma?

There is controversy about the role of beta-agonists in asthma mortality, and the impact of asthma management plans remains unclear. We compared blood beta-agonist levels in patients dying from asthma with those in controls, and estimated the risks associated with specific classes of medication and patterns of management. We identified 89 asthma deaths and recruited 322 patients presenting to hospitals with acute asthma. A questionnaire was administered to the next of kin in 51 cases, and to 202 controls. Blood drawn from 35 cases and 229 controls was assayed for salbutamol. Smoking, drinking, and family problems were significantly more likely among the cases of asthma death than among the controls. The two groups were reasonably well matched with regard to markers of chronic asthma severity. Cases of asthma death were significantly less likely than controls to use a peak flow meter. Written action plans were associated with a 70% reduction in the risk of death. Use of nebulized bronchodilators or oral steroids was significantly more likely in cases of asthma death. Mean blood salbutamol concentrations were 2.5 times higher in cases of asthma. The use of oral steroids for an attack of asthma reduced the risk of death by 90%. More widespread adoption of written asthma management plans, with less reliance on beta-agonists and closer medical supervision, should reduce asthma mortality.

Case-control study of severe life threatening asthma (SLTA) in adults: demographics, health care, and management of the acute attack

BACKGROUND

Severe life threatening asthma (SLTA) is important in its own right and as a proxy for asthma death. In order to target hospital based intervention strategies to those most likely to benefit, risk factors for SLTA among those admitted to hospital need to be identified. A case-control study was undertaken to determine whether, in comparison with patients admitted to hospital with acute asthma, those with SLTA have different sociodemographic and clinical characteristics, evidence of inadequate ongoing medical care, barriers to health care, or deficiencies in management of the acute attack.

METHODS

Seventy seven patients with SLTA were admitted to an intensive care unit (pH 7.17 (0.15), PaCO(2) 10.7 (5.0) kPa) and 239 matched controls (by date of index attack) with acute asthma were admitted to general medical wards. A questionnaire was administered 24-48 hours after admission.

RESULTS

The risk of SLTA in comparison with other patients admitted with acute asthma increased with age (odds ratio (OR) 1.04/year, 95% CI 1.01 to 1.07) and was less for women (OR 0.36, 95% CI 0.20 to 0.68). These variables were controlled for in all subsequent analyses. There were no differences in other sociodemographic features. Cases were more likely to have experienced a previous SLTA (OR 2.04, 95% CI 1.20 to 3.45) and to have had a hospital admission in the last year (OR 1.86, 95% CI 1.09 to 3.18). There were no differences between cases and controls in terms of indicators of quality of ongoing asthma specific medical care, nor was there evidence of disproportionate barriers to health care. During the index attack cases had more severe asthma at the time of presentation, were less likely to have presented to general practitioners, and were more likely to have called an ambulance or presented to an emergency department. In terms of pharmacological management, those with SLTA were more likely to have been using oral theophylline (OR 2.14, 95% CI 1.35 to 3.68) and less likely to have been using inhaled corticosteroids in the two weeks before the index attack (OR 0.69, 95% CI 0.47 to 0.99). While there was no difference in self-management knowledge or behaviour scores, those with SLTA were more likely to have inappropriately used oral corticosteroids during the acute attack (OR 2.09, 95% CI 1.02 to 4.47).

CONCLUSIONS

In comparison with those admitted to hospital with acute severe asthma, patients with SLTA were indistinguishable on sociodemographic criteria (apart from male predominance), were more likely to have had a previous SLTA or hospital admission in the previous year, had similar quality ongoing asthma care, had no evidence of increased physical, economic or other barriers to health care, but had demonstrable deficiencies in the management of the acute index attack. Educational interventions, while not losing sight of the need for good quality ongoing care, should focus on providing individual patients with better advice on self-management of acute exacerbations.

Declining incidence of episodes of asthma: a study of trends in new episodes presenting to general practitioners in the period 1989-98

BACKGROUND

A study was undertaken to determine trends in the incidence of new episodes of asthma presented to general practitioners participating in the Weekly Returns Service of the Royal College of General Practitioners, comprising 92 practices with a registered population of approximately 680 000 persons well distributed throughout England and Wales. These practices monitor the morbidity presented at every consultation, distinguishing between new episodes of illness and ongoing consultations.

METHODS

Age specific weekly rates of new episodes of asthma (and of acute bronchitis) presenting to the general practitioners over the years 1989-98 were examined in four week blocks and analysed by multiple regression, separating secular from seasonal trends.

RESULTS

Quadratic trends in episodes of asthma were evident in each of the age groups with peaks in 1993/4. Corresponding analyses for acute bronchitis disclosed similar trends generally peaking in the winter of 1993/4. Mean weekly incidence data (all ages combined) decreased in all quarters since 1993. Regional analysis (North/Central/South) showed similar decreases.

CONCLUSIONS

There has been a gradual decrease in the incidence of asthma episodes and of acute bronchitis presenting to general practitioners since 1993. The trend of an increase before 1993 followed by a decrease cannot be explained by changes in the patterns of health care usage or diagnostic preference of doctors.

Risk factors for asthma deaths: a population-based, case-control study

OBJECTIVES

To investigate risk factors for death from asthma using a case-control study design with two control groups.

METHODS

Cases (n = 42) comprised subjects aged 10-59 years who died from asthma. Two control groups were selected: a random sample of asthmatics from the community (n = 132) and age and sex matched patients recently admitted to hospital for asthma (n = 89). We obtained information from proxies of cases and controls, and their general practitioners, by a structured telephone survey. Matched and unmatched logistic regression analyses were used to determine odds ratios for risk factors for asthma deaths.

RESULTS

Compared to community controls, important risk factors for asthma deaths included indicators of asthma severity, use of three or more groups of asthma medications, more extensive use of health services for asthma, poor compliance with asthma medications and regularly missing hospital and general practitioner appointments for asthma. Compared to hospital controls, risk factors for asthma deaths were previous visits to emergency department for asthma, knowledge about asthma medications and regularly missing general practitioner appointments.

CONCLUSIONS

In this study, severity of asthma, increased health service utilisation and suboptimal asthma self-management were associated with increased risks for asthma death.

IMPLICATIONS

People with severe asthma or poorly controlled asthma have a greater risk of dying from their asthma. Both clinicians and non-clinicians managing asthma should regularly assess the appropriateness of management to prevent deaths.

An antiinflammatory effect of salmeterol, a long-acting beta(2) agonist, assessed in airway biopsies and bronchoalveolar lavage in asthma

The addition of long-acting beta(2) agonists to inhaled corticosteroid (ICS) therapy in symptomatic patients with asthma improves clinical status more than increasing the dose of ICS. It has been suggested that these benefits could be at the cost of an increase in airway inflammation, but few histopathological studies have been performed in the relevant group. In a double-blind, parallel-group, placebo-controlled study, we randomly assigned 50 symptomatic patients with asthma who were receiving ICS (range, 100 -500 microgram/d) to 12 wk of supplementary treatment with salmeterol (50 microgram twice daily) or fluticasone (100 microgram twice daily) or placebo. Bronchial biopsies and BAL were obtained from 45 patients before and after treatment and analyzed. After treatment with salmeterol there was no deterioration of airway inflammation as assessed by mast cells, lymphocytes, or macrophages in BAL or biopsies, but rather a significant fall in EG1-positive eosinophils in the lamina propria (from a median 18.3 to 7.6 cells/mm, p = 0.01), which was not seen after treatment with fluticasone. The only cellular effect of added fluticasone was a decrease in BAL lymphocyte activation. There was a concurrent improvement in clinical status, more marked with salmeterol than with increased ICS. Thus, adding salmeterol to ICS is not associated with increased "allergic" airway inflammation, but conversely with a complementary antieosinophil effect.

Risk factors for death from asthma. Prairie Provinces Asthma Study Group

BACKGROUND

Asthma mortality rates have increased in Canada and worldwide. Within Canada, the highest rates were seen in the prairie provinces.

OBJECTIVE

The objective was to determine risk factors for fatal asthma by comparing those who died of an acute exacerbation with those who attended an emergency department for treatment of asthma.

METHODS

The case-control study included all deaths from asthma among those aged 5 to 50 years in Alberta, Saskatchewan and Manitoba from November, 1992 through October, 1995 (cases). The 35 fatalities were matched to 209 controls by age, gender, time of the index event and residence.

RESULTS

Cases were more likely than controls to have had severe asthma, an unscheduled physician visit in the past year, a past hospitalization for asthma, and to have been intubated. Both groups reported frequent, regular asthma symptoms. Beta-agonist bronchodilator use was more common among cases, as was use in excess of prescribed amounts. Use of inhaled steroids did not differ between groups. Prior to the index event controls were more likely to report a cold or flu (OR = 0.27; 95% CI: 0.10 to 0.72) and that medications were "not working" (OR = 0.30; 95% CI: 0.12 to 0.71). Cases were more often sad and depressed (OR = 2.88; 95% CI: 1.03 to 8.05). Time between onset/recognition of symptoms and the event was significantly shorter for cases than controls.

CONCLUSIONS

Both groups tolerated high levels of regular symptoms, suggesting poor management. Opportunities for intervention existed for both groups near the time of the event. The short time between recognition of symptoms and death suggests patients at increased risk should monitor their condition closely and take action in response to predetermined criteria.

Use of observational databases to evaluate the effectiveness of antiretroviral therapy for HIV infection: comparison of cohort studies with randomized trials. EuroSIDA, the French Hospital Database on HIV and the Swiss HIV Cohort Study Groups

OBJECTIVES

It is important to assess the extent of bias when comparing the clinical efficacy of antiretroviral regimens in observational databases because, with the current lack of planned large trials, such analyses may represent the only means of assessing the risk of serious clinical events associated with new regimens. We aimed to compare the results from observational databases with those from randomized trials.

METHODS

Three treatment comparisons from randomized trials [Delta, AIDS Clinical Trials Group (ACTG) 175, Community Programs for Clinical Research on AIDS (CPCRA) 007 and ACTC 320] were mimicked in cohorts: (i) zidovudine monotherapy versus combination regimens of two nucleoside analogues; (ii) zidovudine combined with either didanosine or zalcitabine; and (iii) a dual combination versus a triple regimen including a protease inhibitor. Data for over 10 000 patients from the French Hospital Database on HIV, the EuroSIDA study and the Swiss HIV cohort study were analysed for each of the comparisons. Progression to AIDS disease or death was analysed in Cox models, adjusting for baseline differences, and results compared with randomized trials.

RESULTS

For comparison (i) the adjusted relative risk estimates from cohorts were between 0.61 and 0.84, favouring combinations over monotherapy, compared with 0.57 to 0.63 for trials. For comparison (ii) relative risk estimates from cohorts ranged from 0.81 to 1.01 compared with 0.77 to 0.92 for trials. For comparison (iii), two of the cohorts showed similar results to the ACTG 320 trial but one indicated a higher risk of progression on triple therapy [relative risk 1.20, 95% confidence interval (CI) 1.01-1.441, in direct contrast to the trial result (relative risk 0.50, 95% CI 0.33-0.76).

CONCLUSION

Serious biases can be present when comparing outcomes from the use of antiretroviral regimens in observational studies. However, such bias is not inevitable and careful interpretation of the results from several observational studies considered together is likely to be informative, guiding the design of new trials.

Trends in asthma mortality in young people in southern Brazil

BACKGROUND

Mortality from asthma increased and is now declining in some countries, but little is known about these trends in South America.

OBJECTIVE

We aimed to assess trends in mortality from asthma in southern Brazil in children and young adults.

METHODS

Death certificates of 425 people in the state of Rio Grande do Sul aged between 5 and 39 years in whom asthma was reported to be the underlying cause of death during the period 1970 to 1992 were reviewed. Population data were available in 10-year age groups. Testing for trends in mortality rates was conducted using linear and log-linear regression procedures.

RESULTS

Asthma mortality rates in the age groups 5 to 19 and 20 to 39 years ranged between 0.04 and 0.39/100,000 and 0.28 to 0.75/100,000, respectively, and were nonuniformly distributed over the study period. The mean annual increase in rate in 5- to 19-year olds was +0.01 (95% CI 0.003 to 0.016), an average annual percentage increase of +6.8% (95% CI 3% to 11%), with a total increase of 352% between 1970 and 1992. This increase was not due to a shift in labeling from bronchitis to asthma. In the 20 to 39-year age group, asthma and bronchitis mortality rates showed no trend to increase or decrease.

CONCLUSIONS

Asthma mortality in southern Brazil is low, but rose significantly between 1970 and 1992 in the 5 to 19-year age group. This trend differs from that found in other states of Brazil and several other Latin American countries. Reasons for this difference remain unclear.

Rapid onset asthma: a severe but uncommon manifestation

BACKGROUND

Studies of asthma death and severe life threatening asthma (SLTA) include reports of patients who had rapid onset asthma. A study was undertaken to determine the relative frequency of rapid (< 6 hours duration) and slow (> or = 6 hours) onset attacks in patients admitted to hospital with acute severe asthma, and to establish whether those with rapid onset asthma differ in terms of risk factors for asthma morbidity and mortality such as indices of asthma severity/control, socioeconomic factors, health care, and psychological factors.

METHODS

A cross sectional study was performed on 316 patients aged 15-49 years admitted with acute severe asthma and interviewed within 24-48 hours of admission.

RESULTS

Patients underestimated the duration of the index attack. Only 27 (8.5%) were classified as rapid onset. There were more men in the rapid onset group than in the slow onset group (52% versus 26%), and there was evidence of socioeconomic advantage in the patients with rapid onset attacks. The rapid onset group had more previous episodes of SLTA and were more likely to present with SLTA, but there was no difference in length of stay in hospital. The rapid onset group were less likely to have presented to a GP during the index attack and were more likely to have used ambulance services. There was no difference between the groups in any psychological or health care measure.

CONCLUSIONS

Rapid onset attacks are an important but uncommon manifestation of asthma that are more likely to present with SLTA in patients who are more likely to have had previous SLTA. Male subjects are at increased risk of rapid onset attacks, and socioeconomic disadvantage, deficiencies in health care (ongoing and acute), and psychological factors are no more common in these patients than in those with attacks of slow onset. These data are consistent with the hypothesis that there is a small proportion of patients with rapid onset severe asthma who do not have the usual risk factors associated with asthma morbidity or mortality, and thus require different management strategies.

Determinants of management errors in acute severe asthma

BACKGROUND

It is hypothesised that, despite recent initiatives to improve asthma self-management including asthma education, detailed investigation of the sequence of events culminating in hospital admission will lead to the identification of important management errors and thus the likelihood that the majority of severe asthma attacks are preventable by currently available strategies, and that psychological, health care and socioeconomic factors are risk factors for such management errors.

METHODS

A cross sectional study was undertaken of 138 patients aged 15-50 years admitted to hospital (general ward or intensive care unit) with acute severe asthma who were assessed within 24-72 hours of admission using a number of previously validated instruments. A detailed history of events of the attack was assessed against predetermined criteria for non or delayed use of oral corticosteroids and non or delayed use of emergency ambulance services.

RESULTS

Subjects had evidence of severe chronic asthma and had acute severe asthma at presentation (n = 90, pH = 7.3 (0.2), PaCO2 = 7.2 (5.0) kPa) but duration of hospital stay was short (3.7 (2.6) days). Serious management errors occurred very frequently and most were deemed to have been made by the patient. Forward stepwise regression revealed that delayed or non-use of oral corticosteroids was predicted independently by lack of paying job (p = 0.02), high total use of inhaled beta agonists in the 24 hours before index admission (p = 0.04), loss of a job in the last year (p = 0.04), low frequency of use of oral corticosteroids in the last year (p = 0.06), concerns during the index attack about medical expenses (p = 0.07), and delay in the use of ambulance services (p = 0.05)--the model being responsible for 23% of the variance. Delayed or non-summoning of emergency ambulance services was predicted independently by total life events (p = 0.03), having something stolen in the last year (p = 0.003), panic during the index attack (p = 0.01), and concerns during the index attack about taking time off work (p = 0.07)--the model being responsible for 21% of the variance.

CONCLUSIONS

The results of this study show that, despite recent educational advances, serious management errors are common in those admitted to hospital with acute severe asthma and that most management errors relate to patient self-management behaviour. Serious management errors are predicted by a variety of socio-economic and psychological factors. While the results of this study are consistent with the widely held view that most acute severe attacks are theoretically preventable, the challenge for the future is to change patients' behaviour in the face of considerable adverse socioeconomic and psychological factors.

International trends in sales of inhaled fenoterol, all inhaled beta-agonists, and asthma mortality, 1970-1992

To evaluate the hypothesis that fenoterol or all inhaled beta-agonists caused an epidemic of asthma mortality in New Zealand from the late 1970s to the mid-1980s, we examined trends from 1970 to 1992 in per capita sales of inhaled fenoterol, inhaled beta-agonists, and asthma mortality in New Zealand and nine other countries that marketed fenoterol. During the last two decades, there has been a large and widespread increase in sales of inhaled beta-agonists, including fenoterol. Asthma mortality in most countries, however, has been relatively stable. Only New Zealand experienced an epidemic of asthma mortality. In addition, sales rates of fenoterol similar in magnitude to those in New Zealand near the peak of the epidemic also occurred in Belgium, Austria, and Germany, while asthma mortality in these countries remained low. Also, sales rates of all beta-agonists in Australia were similar to those in New Zealand, but no epidemic of asthma mortality occurred in Australia. Therefore, the difference between asthma mortality rates in New Zealand and other countries is not explained by differences in per capita sales of fenoterol or all beta-agonists. Within New Zealand, the beginning and end of the epidemic correlated with a rise and fall in sales of all beta-agonists, including fenoterol. From 1980 to 1989, however, sales of fenoterol and all beta-agonists doubled in New Zealand while asthma mortality declined by 40%. International data on medication sales and asthma mortality, therefore, do not point to a relation between asthma mortality and beta-agonists in general nor fenoterol in particular.

The association between asthma drugs and severe life-threatening attacks

OBJECTIVES

To measure the association between asthma drugs and death or ICU admission due to asthma (severe life-threatening attack of asthma [SLTA]), and to assess the possibility that these associations may not be causal but due to the prescription of these drugs to patients with more severe disease (confounding).

DESIGN

Retrospective cohort study of 655 asthmatics who attended an emergency department in 1986 to 1987 followed till death or May 1989.

METHODS

Outcome events were death or ICU admission due to asthma (SLTA). All hospital attendances were identified and patients classified at each according to drug exposure and a wide variety of measures of asthma severity. Incidence rates were computed as total outcome events divided by person-time contributed for each subject classified according to drug use and asthma severity. Rate ratio (RR) estimates for severe asthma outcomes associated with use as compared to nonuse of asthma drugs were calculated. Severity markers were identified and used to adjust the crude RR estimates.

RESULTS

One hundred five SLTAs (15 deaths, 90 ICU admissions) occurred in 66 patients. Like inhaled fenoterol, oral beta-agonists, theophylline, cromolyn, inhaled steroids, and oral steroids were all associated with an increased risk of SLTA. When adjusted progressively for measures of severity, these increased risks became insignificant except for cromolyn.

CONCLUSION

Unadjusted RR estimates for severe asthma events comparing exposure to a particular drug with nonuse are overestimates due to confounding. Control with two severity markers (hospital admission in the last year, use of oral corticosteroid at the time of previous admission) removes some confounding but control for additional severity markers not available in previous studies reduces the effect estimates further. These results suggest that the problem of confounding is substantial in nonrandomized epidemiologic studies of asthma drugs. Previous studies reporting RR estimates are likely to be confounded.

Characterisation of asthma management in the Fallon Community Health Plan from 1988 to 1991

In order to characterise asthma management in a managed care setting, we identified 10,301 patients who were diagnosed with asthma between 1 January 1988 and 31 December 1991 at a group model health maintenance organisation in central Massachusetts, US. We obtained for these patients automated utilisation files containing data on medications, hospitalisations, emergency room visits, office visits, and estimated costs of these services. The medication dispensed to the greatest proportion of patients was beta 2 agonists either by inhalation (56%) or orally (21%). Theophylline was dispensed to 23% of the patients. Maintenance therapy was inhaled anti-inflammatory medication was uncommon, as inhaled corticosteroids (17%) and sodium cromoglycate (cromolyn sodium) [8%] were dispensed to fewer patients than other asthma medications. Among patients who had been hospitalised in the previous year, 36% were presently receiving inhaled corticosteroids, and among patients who used at least one beta 2 agonist metered-dose inhaler per month, 49% were presently receiving inhaled corticosteroids. Economic analyses showed that only 8% of the patients had either a hospital admission or an emergency room visit, but hospital costs among these patients accounted for 25% of the total costs of asthma care. In addition, the top 10% most expensive patients accounted for 42% of the total cost of asthma care. We conclude that a substantial proportion of patients at increased risk of a severe attack, by virtue of having a recent hospitalisation, do not receive maintenance anti-inflammatory therapy, and that hospitalisations among a relatively small proportion of asthma patients contribute significantly to the cost of asthma care.