Abstract
BackgroundImproved understanding of the normal range of blood eosinophil counts (BEC) and conditions that influence them in non-asthmatic individuals should allow more accurate estimation of the threshold at which eosinophilic disease should be considered, diagnosed, and treated. This analysis investigated the impact of atopy, smoking, and parasitic infection on BEC. MethodsThis was a post hoc analysis of non-asthmatic subjects from a case-control study (CONEP 450/10) conducted at the Program for Control of Asthma in Bahia (ProAR). Participant BECs were measured at baseline; correlations between predefined risk factors and BEC were assessed via univariate and stratified analysis. ResultsOf the 454 participants included, 3% were helminth parasite-positive, 18% were non-helminth parasite-positive; and 450 had BEC data. The median (interquartile range [IQR]) BEC was 152 (96, 252) cells/μL. Any positive skin prick test, elevated total immunoglobulin E, allergic rhinitis, and being a current smoker were all individually associated with higher BEC (p < 0.05) compared with BEC in participants without these factors, but having a non-helminthic parasitic infection was not. Participants with all 4 risk factors that were associated with higher BEC had a median (IQR) BEC of 192 cells/μL (94, 416) versus 106 cells/μL (70, 164) for those with no risk factors. ConclusionsIn non-asthmatic subjects, atopy, allergic rhinitis, and current smoking status were associated with higher BEC compared with subjects without these factors, but BEC values were well below the threshold commonly accepted as normal. Therefore, BEC should be interpreted in the context of an individual's medical conditions and other BEC-influencing factors.
Highlights
Improved understanding of the normal range of blood eosinophil counts (BEC) and conditions that influence them in non-asthmatic individuals should allow more accurate estimation of the threshold at which eosinophilic disease should be considered, diagnosed, and treated
Any positive skin prick test, elevated total immunoglobulin E, allergic rhinitis, and being a current smoker were all individually associated with higher BEC (p < 0.05) compared with BEC in participants without these factors, but having a non-helminthic parasitic infection was not
In non-asthmatic subjects, atopy, allergic rhinitis, and current smoking status were associated with higher BEC compared with subjects without these factors, but BEC values were well below the threshold commonly accepted as normal
Summary
Improved understanding of the normal range of blood eosinophil counts (BEC) and conditions that influence them in non-asthmatic individuals should allow more accurate estimation of the threshold at which eosinophilic disease should be considered, diagnosed, and treated. This analysis investigated the impact of atopy, smoking, and parasitic infection on BEC. It is apparent that blood eosinophil count is a marker of response to corticosteroids and anti-interleukin (IL)-5 treatment in a range of airway diseases, asthma and chronic obstructive pulmonary disease (COPD).. The level of eosinophils considered to be predictive of treatment response in these conditions is considerably lower than the 450 cells/mL threshold cited in the literature.. 450 cells/mL are generally considered to be abnormal. It is apparent that blood eosinophil count is a marker of response to corticosteroids and anti-interleukin (IL)-5 treatment in a range of airway diseases, asthma and chronic obstructive pulmonary disease (COPD). the Global Strategy for Asthma Management and Prevention (Global Initiative for Asthma [GINA]) guidelines list elevated blood eosinophil count as one of the modifiable risk factors for asthma exacerbations, and they recommend that the presence/absence of elevated eosinophil counts is used to help inform treatment decisions. Evidence indicates a relationship between elevated blood eosinophil counts, exacerbations of COPD, and the responsiveness of COPD exacerbations to treatment. the level of eosinophils considered to be predictive of treatment response in these conditions is considerably lower than the 450 cells/mL threshold cited in the literature. An understanding of factors that may influence blood eosinophil count is, of increasing importance
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