Inner City Severe Allergic Asthma: Differential Clinical Markers in Eosinophilic Low Cohort (LC, <150 uL) vs Medium Cohort (MC, 150-300 uL) vs High Cohort (HC, > 300 uL)

RATIONALE: An eosinophil count of >150/uL is considered a threshold for anti-IL-5 therapy in uncontrolled severe asthma. We hypothesized that stepwise increases in eosinophilia serve as a marker for high IgE levels, allergen sensitizations, rhinitis, worsening obstruction and exacerbations in asthmatics.

METHODS: Inner city severe asthmatic subjects were divided into three eosinophil Cohorts, Low (LC), Medium (MC) and High (HC) matched for age and BMI. Pulmonary function tests, IgE levels, allergen sensitizations (ImmunoCAP®), exacerbations, rhinitis and smoking history were examined. Exclusion criteria included age < 18 years, ABPA, smoking > 10 pack years and COPD.

RESULTS: LC (n=39), MC (n=32) & HC (n=31) had statistically different eosinophil counts (uL, x ± SD) 65 ± 52, 237 ± 41, 505 ± 189 41 (p=0.001 LC vs MC and p=<0.001 MC vs HC) and IgE levels (IU/ml, x ± SD) 20 ± 15, 146 ± 294, and 550 ± 888 (p=0.01 LC vs MC and p=<0.001 MC vs HC). MC vs LC, though not HC showed increased association with smoking (p=0.045), sensitization to Dermatophagoides (dust mite, p=0.04) and maple (p= 0.02). Dog, ragweed and oak were associated with HC compared to MC (p= 0.04, 0.009, 0.009) but not MC vs LC. Surprisingly, we failed to find significant cohort differences in cat, cockroach, obstruction, exacerbations, oral steroid, rhinitis or chronic cough.

CONCLUSIONS:

In inner city severe asthmatics, increasing eosinophilia was significantly associated with IgE levels, smoking, allergic sensitization to dust mite, dog, ragweed, maple and oak, but surprisingly not to cat, cockroach, airway obstruction, exacerbations or cough.