section name header

Evidence summaries

Interventions Based on Sputum Eosinophils for Asthma

Tailored asthma interventions based on sputum eosinophils appear to be beneficial in reducing the frequency of asthma exacerbations and hospitalisations in adults. Level of evidence: "B"

The quality of evidence is downgraded by imprecise results (few outcome events and wide confidence intervals).

Summary

A Cochrane review [Abstract] 1 included 6 studies (5 in adults and 1 involving children/adolescents) with a total of 374 subjects. The studies varied in the sputum eosinophil levels (ranging from 2% to 8%) and algorithms used to adjust medications. The duration of the studies varied from 6 to 24 months.

There was a significant reduction in the occurrence of any exacerbations when treatment was based on sputum eosinophil counts, compared to that based on clinical symptoms with or without lung function (OR 0.57, 95% CI 0.38 to 0.86; 4 studies, n=269). The risk of having one or more exacerbations over 16 months was 82% in the control arm and 62% in the sputum strategy arm (OR 0.36, 95% CI 0.21 to 0.62; 4 studies, n=269), resulting in a number needed to treat to benefit (NNTB) of 6 (95% CI 4 to 13).The risk of one or more hospitalisations over 16 months was 24% in controls compared to 8% in the sputum arm (OR 0.28, 95% CI 0.09 to 0.84; 4 studies, n=269). Clinical symptoms, quality of life and spirometry were not significantly different between groups, and the mean dose of inhaled corticosteroids per day was also similar in both groups. The included studies did not record any adverse events.

In the subgroup analyses, for children the reductions seen between the sputum eosinophil strategy and control strategy for occurrence of any exacerbations (RR 0.75, 95% CI 0.54 to 1.04; 1 study, n=54), number of participants who had one or more episodes of asthma exacerbation (OR 0.39, 95% CI 0.09 to 1.71; 1 study, n=54) or exacerbations requiring hospitalisations (OR 0.38, 95% CI 0.10 to 1.45; 1 study, n=54) did not achieve statistical significance (possibly due to lack of statistical power due to small numbers).

Note: There is insufficient data for or against tailoring asthma medications based on sputum eosinophilia in children. Adults with frequent exacerbations and severe asthma may derive the greatest benefit from this additional monitoring test, although it was not possible to confirm this through subgroup analysis. Studies using newer biologic compounds for eosinophilic diseases did not fulfil the inclusion criteria and hence this review cannot be extrapolated to these agents (e.g. anti-interleukin-5).

    References

    • Petsky HL, Li A, Chang AB. Tailored interventions based on sputum eosinophils versus clinical symptoms for asthma in children and adults. Cochrane Database Syst Rev 2017;8():CD005603. [PubMed]

Primary/Secondary Keywords