Tailored interventions based on sputum eosinophils versus clinical symptoms for asthma in children and adults

Pharmacological treatment of asthma is tailored based on various subjective or objective outcome measures. The objective of this review was to evaluate the efficacy of tailoring asthma interventions based on sputum eosinophils in comparison to clinical symptoms for asthma related health outcomes in children and adults. Three trials involving 246 adults fulfilled the predetermined criteria but there were no studies in children. Tailored asthma interventions based on sputum eosinophils is beneficial in reducing the frequency and severity of asthma exacerbations in adults with asthma. This review supports the use of sputum eosinophils to tailor asthma therapy only for adults in reducing the frequency and severity of asthma exacerbations. However, as data for clinical symptoms, quality of life and spirometry were not different between the groups, use of sputum eosinophilia cannot be advocated in all settings until more studies are available. As there were no studies in children, no recommendation can be made for children with asthma.

Authors' conclusions: 

Tailored asthma interventions based on sputum eosinophils is beneficial in reducing the frequency of asthma exacerbations in adults with asthma. This review supports the use of sputum eosinophils to tailor asthma therapy for adults with frequent exacerbations and severe asthma. Further studies need to be undertaken to strengthen these results and no conclusion can be drawn for children with asthma.

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Background: 

Asthma severity and control can be measured both subjectively and objectively. Sputum analysis for evaluation of percentage of sputum eosinophilia directly measures airway inflammation, and is one method of objectively monitoring asthma. Interventions for asthma therapies have been traditionally based on symptoms and spirometry.

Objectives: 

To evaluate the efficacy of tailoring asthma interventions based on sputum analysis in comparison to clinical symptoms (with or without spirometry/peak flow) for asthma related outcomes in children and adults.

Search strategy: 

We searched the Cochrane Airways Group Specialised Register of Trials, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and reference lists of articles. The last search was conducted in November 2008.

Selection criteria: 

All randomised controlled comparisons of adjustment of asthma therapy based on sputum eosinophils compared to traditional methods (primarily clinical symptoms and spirometry/peak flow).

Data collection and analysis: 

Results of searches were reviewed against pre-determined criteria for inclusion. Three sets of reviewers selected relevant studies. Two review authors independently assessed trial quality extracted data. Authors were contacted for further information but none were received. Data were analysed as "treatment received" and sensitivity analyses performed.

Main results: 

Three adult studies were included; these studies were clinically and methodologically heterogenous (use of medications, cut off for percentage of sputum eosinophils and definition of asthma exacerbation). There were no eligible paediatric studies. Of 246 participants randomised, 221 completed the trials. In the meta-analysis, a significant reduction in number of participants who had one or more asthma exacerbations occurred when treatment was based on sputum eosinophils in comparison to clinical symptoms; pooled odds ratio (OR) was 0.49 (95% CI 0.28 to 0.87); number needed to treat to benefit (NNTB) was 6 (95% CI 4 to 32).

There were also differences between groups in the rate of exacerbation (any exacerbation per year) and severity of exacerbations defined by requirement for use of oral corticosteroids but the reduction in hospitalisations was not statistically significant. Data for clinical symptoms, quality of life and spirometry were not significantly different between groups. The mean dose of inhaled corticosteroids per day was similar in both groups and no adverse events were reported. However sputum induction was not always possible.

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