Abstract: Twenty trials were selected for inclusion in the primary analysis (13 paediatric, seven adult), with a total number of 1403 patients. Patients treated with ICS were less likely to be admitted to hospital (OR 0.44; 95% CI 0.31 to 0.62; 12 studies; 960 patients) and heterogeneity (I2 = 27%) was modest. This represents a reduction from 32 to 17 hospital admissions per 100 patients treated with ICS in comparison with placebo. Subgroup analysis of hospital admissions based on concomitant systemic corticosteroid use revealed that both subgroups indicated benefit from ICS in reducing hospital admissions (ICS and systemic corticosteroid versus systemic corticosteroid: OR 0.54; 95% CI 0.36 to 0.81; 5 studies; N = 433; ICS versus placebo: OR 0.27; 95% CI 0.14 to 0.52; 7 studies; N = 527). However, there was moderate heterogeneity in the subgroup using ICS in addition to systemic steroids (I2 = 52%). Patients receiving ICS demonstrated small, significant improvements in peak expiratory flow (PEF: MD 7%; 95% CI 3% to 11%) and forced expiratory volume in one second (FEV1: MD 6%; 95% CI 2% to 10%) at three to four hours post treatment). Only a small number of studies reported these outcomes such that they could be included in the meta-analysis and most of the studies in this comparison did not administer systemic corticosteroids to either treatment group. There was no evidence of significant adverse effects from ICS treatment with regard to tremor or nausea and vomiting. In the secondary analysis of studies comparing ICS alone versus systemic corticosteroid alone, heterogeneity among the studies complicated pooling of data or drawing reliable conclusions. ICS therapy reduces hospital admissions in patients with acute asthma who are not treated with oral or intravenous corticosteroids. They may also reduce admissions when they are used in addition to systemic corticosteroids; however, the most recent evidence is conflicting. There is insufficient evidence that ICS therapy results in clinically important changes in pulmonary function or clinical scores when used in acute asthma in addition to systemic corticosteroids. Also, there is insufficient evidence that ICS therapy can be used in place of systemic corticosteroid therapy when treating acute asthma. Further research is needed to clarify the most appropriate drug dosage and delivery device, and to define which patients are most likely to benefit from ICS therapy. Use of similar measures and reporting methods of lung function, and a common, validated, clinical score would be helpful in future versions of this meta-analysis.

Plain-language summary: This review found that inhaled corticosteroids used alone or in combination with systemic corticosteroids helped to relieve asthma attacks, were well tolerated and had few side effects. However, the most effective drug and dosage are unclear. The studies in the review included a variety of ICSmedications: beclomethasone (Beclovent/Becloforte/QVAR), budesonide (Pulmicort), dexamethasone sodium phosphate, fluticasone propionate (Flovent or Flixotide), Flunisolide (Aerobid) and triamcinolone (Azmacort). The review also found that ICS administered in this setting resulted in fewer hospital admissions. There was a reduction from 32 to 17 hospital admissions per hundred patients treated with ICS agents compared with placebo. At this time there is insufficient evidence to support using ICS agents alone as a replacement for systemic corticosteroid therapy in acute asthma attacks However, there are many unanswered questions about the use of ICS in the emergency department treatment setting. Future research should focus on optimal dosage, dosage frequency and delivery device, identification of effective ICS agents, clearly defined outcomes (such as admissions criteria, pulmonary function testing and follow-up after discharge from emergency departments).