The role of basophils in asthma remains largely unexplored, particularly in population-based studies.
Adults with data on asthma and white blood cell counts from the French CONSTANCES cohort were included. Current asthma (CA) was defined by reports in the last 12 months of asthma attacks, symptoms or treatments. Blood eosinophil (0.25x109/L) and neutrophil (5x109/L) cut-offs defined paucigranulocytic (P), neutrophilic (N), eosinophilic (E) and mixed (M) asthma phenotypes. Percentile75(0.054x109/L), Perct90(0.072x109/L) and Perct97.5(0.1x109/L) basophil cut-offs were used. Cross-sectional associations of basophils with asthma characteristics and phenotypes were studied using logistic models. Confounders were age, sex, smoking status, education level, French deprivation index, treatment and body mass index.
Basophil count range was 0.027 to 0.43x109/L (177,304 adults, 47 years old, 54% women, 17% smokers, 13% ever-asthma), and higher in ever-asthmatics than in never-asthmatics (adjusted(a)mean: 0.044 vs 0.042x109/L, P<10-4). Among CA (n=16000, 6%N, 32%E, 4%M), significant correlations were found between basophil with eosinophil (r=0.27) or neutrophil counts (r=0.15). Basophil count differed according to phenotypes ((a)means: 0.041, 0.047, 0.053 and 0.055x109/L in P, N, E and M, P<10-4). High basophil count was associated with a higher risk of woken by an attack of cough among CA (aOR=1.08[1.00-1.17], 1.07[0.97-1.19], 1.15[0.95-1.39] for the 3 cut-offs), and specifically among CA with E (but not P, N and M) phenotype (aOR=1.21[1.07-1.36], 1.22[1.05-1.42], 1.42[1.10-1.84]).
These preliminary results suggest an actual role of basophils as actors and potential biomarkers in asthma. Unsupervised analyses are on-going.