Eosinophil count and efficacy of omalizumab treatment

摘要

To the Editor:I read with interest the article by Busse et al1 assessing the effect of omalizumab in a group of asthmatic patients in relation to their eosinophil counts. In their well-performed study they found that the primary end point (a decrease in asthma exacerbations) was not met. In the subgroup analysis, according to the eosinophil count (low, <300 cells/mL; high, >300 cells/ mL), they were able to demonstrate efficacy in patients within the high-count group.It is intriguing that the primary end point was not achieved despite omalizumab being a proved therapy for allergic asthma. To understand this paradox, it is necessary to take a closer look at this study. First, they chose patients who, despite being symptomatic, had normal lung function (FEV1 >80%). Second, prior use of systemic corticosteroids (oral or intravenous), a classic sign of severity, was an exclusion and not an inclusion criteria.Finally, after carefully reading the article and the additional information in the article's Online Repository, I did not find any reference about the allergens to which these patients were allergic. Defining asthma as atopic based only on the serum total IgE level (30-1300 IU/mL), as apparently was done, is certainly not enough.The authors should clarify this last point and, if they have this information, plot it against the eosinophil level. It would probably show that (as expected) patients with positive results to allergen did much better than patients with negative results to allergen and had the highest eosinophil counts.Once again, this study also shows that those who derive the most benefit from omalizumab have atopic asthma that is symptomatic despite optimal treatment, are in need of frequent steroid bouts, and have abnormal lung function test results.