High blood eosinophil count is associated with more frequent asthma attacks in asthma patients.
BACKGROUND
The clinical importance of eosinophils in asthma has been shown by the observation of frequent exacerbation in patients with high sputum eosinophil counts and a corresponding decrease in exacerbations when anti-inflammatory therapy was adjusted to maintain low sputum eosinophil percentages. However, less is known of the relation between blood eosinophilia and asthma exacerbation.


OBJECTIVE
To examine whether patients with asthma and a higher blood eosinophil count have more asthma attacks than those with a lower count.


METHODS
The authors analyzed data from the National Health and Nutrition Examination Survey, an annual cross-sectional survey of the US general population. Patients with asthma and asthma attacks were identified based on participants' self-report or parental report. A high blood eosinophil count was defined using 200, 300, or 400 cells/μL as cutoffs. The primary analysis used data from 2001 through 2010 after adjusting for demographic variables, obesity, smoking, neutrophil level, and past treatment for wheezing. A secondary analysis used data from 2007 through 2010 and included recent treatment for asthma and fraction of exhaled nitric oxide level as additional adjustment variables.


RESULTS
In survey years 2001 through 2010, 3,162 patients with asthma had blood eosinophil data and approximately half (54% of children and 52% of adults) reported an asthma attack in the previous year. In the primary analysis, higher blood eosinophil counts were associated with more asthma attacks in children but not in adults. The secondary analysis suggested an association in both children and adults.


CONCLUSIONS
Patients with asthma with higher blood eosinophil counts experienced more asthma attacks than those with lower eosinophil counts.
Observational Research Center, AstraZeneca, Gaithersburg, Maryland. Electronic address: trantr@medimmune.com.
Trung N
TN
Tran
Translational Sciences, MedImmune, Gaithersburg, Maryland.
Deepak B
DB
Khatry
Observational Research Center, AstraZeneca, Gaithersburg, Maryland.
Xiongkan
X
Ke
Translational Sciences, MedImmune, Gaithersburg, Maryland.
Christine K
CK
Ward
Clinical Development, MedImmune, Gaithersburg, Maryland.
David
D
Gossage
D000293:Adolescent; D000328:Adult; D000818:Animals; D018926:Anti-Allergic Agents / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy / Q000453:epidemiology / Q000276:immunology / Q000473:pathology*; D002648:Child; D015897:Comorbidity; D006801:Humans; D007958:Leukocyte Count; D008875:Middle Aged; D020556:Neutrophil Infiltration / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology / Q000473:pathology*; D009749:Nutrition Surveys; D009765:Obesity / Q000188:drug therapy / Q000453:epidemiology / Q000276:immunology / Q000473:pathology*; D012135:Respiratory Sounds / Q000276:immunology; D012907:Smoking; D014481:United States / Q000453:epidemiology
D018926:Anti-Allergic Agents