Phenotypic Features Compared According to VHI % Quartiles
Children with VHI % in the upper quartile had phenotypic features unique from those in children in the lower quartile (Table I and Figure 2). Children with VHI % in the upper 75th %ile had greater non-white racial/ethnic backgrounds (73% vs 20%, p = .006), more lifetime ICU admissions (range of 0-6 vs 0-4, p = .04), and were treated with twice the number of daily controller medications (4.0 vs 2.0 , p = .02) compared to children in the lower 25th%ile.
Accordingly, children with VHI % in the upper 75th%ile had reduced lung function with greater airflow limitation and bronchodilator responsiveness compared to children in the lower 25th %ile (Table I). Differences included lower pre-BD FEV1 % (80 vs 100, p = .02), and lower pre-BD FEV­1­/FVC % (83 vs 94, p = .04) in children with the upper 25th %ile VHI %. Both the pre- and post-BD FEF25-75 % (55 vs 89 and 61 vs 91, respectively, p < .05 for both) were less than mid-flows in children with VHI % in the lower 25th %ile. Furthemore children with VHI % in the upper 75th %ile had overall greater bronchodilator reversibility, and the % change in the FEV­1­ % from baseline was higher in the 75th versus 25th-75th %iles (22 vs 11, p = .01).
VHI % sub-groups likewise had difference in the magnitude of type 2 inflammatory markers (Table I). Children with VHI % in the 75th %ile had higher absolute eosinophil counts (620 cells/ ul vs 220 cells/ ul blood, p = .001), a higher proportion with absolute eosinophil counts ≥ 300 cells/ul blood (87% versus 20%, p = .001) and higher FeNO (36 ppb vs 22 ppb, p = .03) compared to lower %iles. VHI % sub-groups did not differentiate total IgE and the number of positive specific IgE tests. Overall correlations between VH indicators and scaled outcomes were modest to poor (See E-supplement, results and Table E-2).