Interventions Based on Sputum Eosinophils for Asthma

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).