Peripheral blood eosinophil counts and bronchial responsiveness.

Bronchial responsiveness (histamine PC20) and peripheral blood eosinophil counts were measured in 23 asthmatic subjects, of whom 14 were atopic and nine non-atopic. In the group as a whole there was an inverse correlation between baseline eosinophil count and histamine PC20 (r = -0.71; p less than 0.001). For atopic subjects a relationship between eosinophil count and histamine PC20 was observed (r = -0.74; p less than 0.01), but there was no correlation between eosinophil count and baseline FEV1 or baseline FEV1 and histamine PC20. For the non-atopic subjects a similar relationship between eosinophil count and histamine PC20 was seen (r = -0.68; p less than 0.05) and a less significant inverse correlation between baseline eosinophil count and baseline FEV1 (r = -0.65; p less than 0.05). These results show a relationship between eosinophil count and non-specific bronchial responsiveness in both atopic and non-atopic asthma.