Changes in blood eosinophil (EOS) count after starting treatment with inhaled corticosteroids can predict response in patients with COPD, a study which appears to turn accepted wisdom on its head has suggested.
Reanalysis of data from the three-year, 700-patient ISOLDE trial, which compared fluticasone propionate 500μg twice daily with placebo, found that EOS levels one year after treatment starting were strongly predictive of whether treatment was working.
Those whose EOS levels had fallen were more likely to show benefit from ICS treatment, the analysis showed, whereas those who had shown an increase in EOS had more exacerbations and a faster rate of decline.
Reporting in the European Respiratory Journal, researchers found that in patients with EOS suppression of ≥200 EOS/μL, ICS use was associated with a decelerated FEV1 decline of around 32mLs/year and a 30% reduction in the exacerbation rate.
If proven in clinical trials, monitoring EOS rate could provide a useful tool for predicting response to ICS and identifying the 20% who not only do not seem to be benefiting but may be doing worse with treatment, the researchers concluded.
Study author Dr Alexander Mathioudakis, NIHR Academic Clinical Fellow and Honorary Lecturer in Respiratory Medicine at The University of Manchester said this was the first time researchers had looked at EOS while patients are already receiving ICS treatment.
“More specifically, we found that a decrease in EOS following treatment with ICS is associated with better clinical response to ICS, while an increase in EOS following treatment with ICS is predictive of a poor clinical response to ICS.
“Patients in the last group, actually appear to be harmed by ICS. In our study, we found that EOS change (increase or decrease) is more accurate in predicting clinical response to ICS than a single EOS measurement, and this is a novel finding.”
He added that another novel – and perhaps concerning – finding was that lower EOS during treatment may actually be associated with better response and vice versa.
“This finding contrasts with the common belief and that means clinical use of EOS at present may be wrong and clinicians may end up giving the wrong treatment advice to some patients.”
He added that the findings would need to be confirmed in other studies but in the meantime, clinicians should keep in mind that decisions to discontinue ICS cannot be solely based on EOS, because the EOS measured while patients are receiving ICS may be inaccurate with counts measured over time.
Professor John Hurst, Professor of Respiratory Medicine at University College London, said while further work was needed, the findings raised some interesting questions.
“The novelty here, as I understand it, is seeing what happens to the eosinophil count once treatment has been started, to guide likely benefit. Of course that would mean the patient coming back for a second visit to have the blood checked again, and this was not a prospective trial but post-hoc, ” he added.