Does blood eosinophilia in wheezing infants predict later asthma? A prospective 18–20-year follow-up

Although eosinophilia in wheezing infants predicts subsequent wheezing, it is not known how long the association persists. Our aim was to evaluate the connection between blood eosinophilia in infancy and later wheezing/asthma until adulthood, with special attention paid to infection-induced changes in blood eosinophils. We have prospectively followed up 83 infants until adulthood after hospitalization for bronchiolitis in 1981-1982. Blood eosinophils were determined in a counting chamber on admission and on convalescence 4-6 weeks later. Data on recurrent wheezing and asthma were registered prospectively at five follow-ups until the age of 18-20 years. The median (25th-75th percentile) eosinophil count was 0.100 x 10E9/L (0.028-0.321) on admission and 0.231 x 10E9/L (0.119-0.368) on convalescence. Eosinophils during bronchiolitis or infection-induced changes in eosinophils were not associated with subsequent wheezing/asthma at any age during the follow-up. The result was similar in univariate and multivariate analyses. Respiratory syncytial virus (RSV) bronchiolitis patients had lower eosinophils on admission than non-RSV cases, but the changes induced by RSV or other infection did not differ significantly. In univariate analyses, elevated eosinophils on convalescence predicted later wheezing until 3-4 years of age. In multivariate analysis, adjusted for RSV etiology, age on admission, and histories of earlier wheezing and atopy, elevated eosinophils on convalescence predicted increased asthma risk at 2-3 years (OR, 2.26; 95% CI, 1.29-3.95), at 3-4 years (OR, 2.24; 95% CI, 1.27-3.95), and at 8.5-10 years (OR, 2.16; 95% CI, 1.01-4.64). Eosinophilia outside, but not during, infection predicted recurrent wheezing until preschool and early school years but not thereafter.