House dust mite control measures for asthma.

BACKGROUND: The major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites. OBJECTIVES: The objective of this review is to assess the effects of reducing exposure to house dust mite antigens in the homes of mite-sensitive asthmatics, assessing chemical and physical methods separately and together. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, checked reference lists of articles and hand-searched Respiration (1980 to 1996) and Clinical and Experimental Allergy (1980 to 1996). The Cochrane Library is searched every three months. SELECTION CRITERIA: Randomised trials of mite control measures vs placebo or no treatment in asthmatic people known to be sensitive to house dust mites. DATA COLLECTION AND ANALYSIS: Two reviewers applied the trial inclusion criteria, assessed their quality and extracted the data independently. Study authors were contacted to clarify information. MAIN RESULTS: Twenty-nine trials (939 patients in the analyses) were included, with two trials awaiting assessment. Nine trials assessed chemical methods alone, 15 physical methods alone, and 5 a combination of chemical and physical methods. Overall, there was no statistically significant difference improvement of asthma (relative risk 1.04, 95% confidence interval 0.83 to 1.31), asthma symptom scores (standardised mean difference -0.07, 95% confidence interval -0.35 to 0.22), medication usage (standardised mean difference -0.14, 95% confidence interval -0.43 to 0.15), or peak flow in the morning (standardised mean difference 0.04, 95% confidence interval -0.13 to 0.21). For chemical methods used alone, there was a statistically significantly adverse effect on symptoms (P = 0.03), whereas for physical methods used alone as evaluated in parallel group trials, there was a statistically significant beneficial effect (P = 0.02). However, because of the large number of significance tests we performed, two significant results would be expected to occur by chance. REVIEWER'S CONCLUSIONS: Currently available evidence from controlled trials of chemical and physical approaches to reducing exposure to house dust mite antigens in the homes of mite-sensitive asthmatics does not provide a secure basis for advice and policy. Further trials - one of them very large - are currently in progress. The additional evidence from these studies will help to clarify whether or not the substantial efforts required to implement strategies intended to reduce mites can be expected to yield beneficial effects of a magnitude that people with mite sensitive asthma consider worthwhile.

Inhaled beta-agonists for asthma in mechanically ventilated patients.

BACKGROUND: A small number of patients with acute severe asthma require intubation and positive pressure ventilation. The beneficial effects of inhaled bronchodilators on acute asthma in spontaneously breathing subjects are well established, but there remain important questions regarding inhaled beta2-agonists, for patients who are intubated and receiving ventilation. OBJECTIVES: To determine the effects of inhaled beta-agonists on asthmatic patients who require intubation and mechanical ventilation. SEARCH STRATEGY: Randomised controlled trials were sought from the Cochrane Airways Group Asthma Register. Primary authors and content experts were contacted to identify eligible studies and bibliographies from known reviews and texts were searched. SELECTION CRITERIA: Randomised, controlled clinical trials involving adult patients with acute asthma, who were intubated and supported with positive pressure ventilation. Studies were to be included if patients were treated with beta2-adrenergic agonist agents and there was a comparator group treated with either placebo, no medication, or 'standard' treatment. DATA COLLECTION AND ANALYSIS: Two reviewers independently examined all identified articles. The full text of any potentially relevant article was reviewed independently by two reviewers. MAIN RESULTS: The search yielded 152 abstracts. Of these, four articles were identified as potential trials. None of the four trials met the inclusion criteria for the review. A further search was conducted in August 2001. No further trials were included in the review. REVIEWER'S CONCLUSIONS: There are no data from randomised controlled trials to provide evidence for or against current practices regarding the use of inhaled beta2-agonists in asthmatic subjects who are intubated and ventilated.

House dust mite control measures for asthma.

BACKGROUND: The major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites. OBJECTIVES: The objective of this review was to assess the effects of reducing exposure to house dust mite antigens in the homes of mite-sensitive asthmatics. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, checked reference lists of articles and hand-searched Respiration (1980 to 1996) and Clinical and Experimental Allergy (1980 to 1996). The Cochrane Library is searched every three months. SELECTION CRITERIA: Randomised trials of mite control measures vs placebo or no treatment in asthmatic people known to be sensitive to house dust mites. DATA COLLECTION AND ANALYSIS: Two reviewers applied the trial inclusion criteria, assessed their quality and extracted the data independently. Study authors were contacted to clarify information. MAIN RESULTS: Twenty-nine trials (939 patients in the analyses) were included, with two trials awaiting assessment. There was little difference in improvement of asthma between patients in experimental groups compared to control groups (relative risk 1.04, 95% confidence interval (95%CI) 0.83 to 1.31). Asthma symptom scores were also similar for the experimental and control groups (standardised mean difference (SMD) -0.07, 95% CI -0.35 to 0.22), however there was significant heterogeneity between studies p=0.015. This appears to have been due, in part, to the parallel group studies of physical treatments. These three studies (107 patients) showed a significant reduction in symptoms; SMD -0.44 (95% CI -0.83, -0.06) with no heterogeneity between the trials. No significant difference was noted for medication usage (SMD -0.14, 95%CI -0.43 to 0.15). Peak flow in the morning showed no significant difference between the experimental and the control groups (SMD 0.04, 95%CI -0.13 to 0.21). REVIEWER'S CONCLUSIONS: Current chemical methods aimed at reducing exposure to house dust mite allergens seem to be ineffective and cannot be recommended as prophylaxis for mite sensitive asthmatics. Physical reduction methods may reduce asthma symptoms, but results of larger and more rigorous studies are required before any recommendations can be made concerning this approach.

House dust mite control measures for asthma.

BACKGROUND: The major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites. OBJECTIVES: The objective of this review was to assess the effects of reducing exposure to house dust mite antigens in the homes of mite-sensitive asthmatics. SEARCH STRATEGY: We searched the Cochrane Airways Group trials register, checked reference lists of articles and hand-searched Respiration (1980 to 1996) and Clinical and Experimental Allergy (1980 to 1996). SELECTION CRITERIA: Randomised trials of mite control measures in asthmatic people known to be sensitive to house dust mites. DATA COLLECTION AND ANALYSIS: Two reviewers applied the trial inclusion criteria and extracted the data independently. One reviewer applied the trial quality assessment criteria. Study authors were contacted to clarify information. MAIN RESULTS: Twenty-three trials were included, with four trials awaiting assessment. There was little difference in improvement of asthma between people in experimental groups compared to control groups (odds ratio 1.2, 95% confidence interval 0.66 to 2.18). Asthma symptom scores were also similar for the experimental and control groups (standardised mean difference -0. 06, 95% confidence interval -0.54 to 0.41). These scores showed a high degree of heterogeneity. No significant difference was noted for medication usage (standardised mean difference -0.14, 95% confidence interval -0.43 to 0.15). Peak flow in the morning showed no significant difference between the experimental and the control groups (standardised mean difference -0.03, 95% confidence interval -0.25 to 0.19). REVIEWER'S CONCLUSIONS: Current chemical and physical methods aimed at reducing exposure to house dust mite allergens seem to be ineffective and cannot be recommended as prophylaxis for mite sensitive asthmatics.

Inhaled beta-agonists for asthma in mechanically ventilated patients.

BACKGROUND: A small number of patients with acute severe asthma require intubation and positive pressure ventilation. The beneficial effects of inhaled bronchodilators on acute asthma in spontaneously breathing subjects are well established, but there remain important questions regarding inhaled beta2-agonists, for patients who are intubated and receiving ventilation. OBJECTIVES: To determine the effects of inhaled beta-agonists on asthmatic patients who require intubation and mechanical ventilation. SEARCH STRATEGY: Randomised controlled trials were sought from the Cochrane Airways Group Asthma Register. Primary authors and content experts were contacted to identify eligible studies and bibliographies from known reviews and texts were searched. SELECTION CRITERIA: Randomised, controlled clinical trials involving adult patients with acute asthma, who were intubated and supported with positive pressure ventilation. Studies were to be included if patients were treated with beta2-adrenergic agonist agents and there was a comparator group treated with either placebo, no medication, or 'standard' treatment. DATA COLLECTION AND ANALYSIS: Two reviewers independently examined all identified articles. The full text of any potentially relevant article was reviewed independently by two reviewers. MAIN RESULTS: The search yielded 152 abstracts. Of these, four articles were identified as potential trials. None of the four trials met the inclusion criteria for the review. REVIEWER'S CONCLUSIONS: There are no data from randomised controlled trials to provide evidence for or against current practices regarding the use of inhaled beta2-agonists in asthmatic subjects who are intubated and ventilated.

House dust mite control measures in the management of asthma: meta-analysis.

OBJECTIVE: To determine whether patients with asthma who are sensitive to mites benefit from measures designed to reduce their exposure to house dust mite antigen in the home. DESIGN: Meta-analysis of randomised trials that investigated the effects on asthma patients of chemical or physical measures to control mites, or both, in comparison with an untreated control group. All trials in any language were eligible for inclusion. SUBJECTS: Patients with bronchial asthma as diagnosed by a doctor and sensitisation to mites as determined by skin prick testing, bronchial provocation testing, or serum assays for specific IgE antibodies. MAIN OUTCOME MEASURES: Number of patients whose allergic symptoms improved, improvement in asthma symptoms, improvement in peak expiratory flow rate. Outcomes measured on different scales were combined using the standardised effect size method (the difference in effect was divided by the standard deviation of the measurements). RESULTS: 23 studies were included in the meta-analysis; 6 studies used chemical methods to reduce exposure to mites, 13 used physical methods, and 4 used a combination. Altogether, 41/113 patients exposed to treatment interventions improved compared with 38/117 in the control groups (odds ratio 1.20, 95% confidence interval 0.66 to 2.18). The standardised mean difference for improvement in asthma symptoms was -0.06 (95% confidence interval -0.54 to 0.41). For peak flow rate measured in the morning the standardised mean difference was -0.03 (-0.25 to 0.19). As measured in the original units this difference between the treatment and the control group corresponds to -3 l/min (95% confidence interval -25 l/min to 19 l/min). The results were similar in the subgroups of trials that reported successful reduction in exposure to mites or had long follow up times. CONCLUSION: Current chemical and physical methods aimed at reducing exposure to allergens from house dust mites seem to be ineffective and cannot be recommended as prophylactic treatment for asthma patients sensitive to mites.

[Randomized clinical trials in the Ugeskrift for Laeger 1948-1995]. / Randomiserede kliniske forsøg i Ugeskrift for Laeger 1948-1995.

The Danish Medical Journal (Ugeskrift for Laeger) was handsearched for randomised and pseudorandomised clinical trials over the years 1948-1995. We found 665 trials of which 539 (81%) were classified as randomised; the randomisation method was not stated for 422 of them (78%) and was insufficiently described in the majority of the rest. This problem became worse with time (p = 0.01). In contrast to the international literature where the increase was more gradual and occurred several years later, the number of randomised trials increased markedly around 1973. This change is associated with the introduction of courses in clinical research methodology during the previous years. Since randomisation is the most important safeguard against bias, the method should be described in detail.