Early Inhaled Corticosteroid Reduction as a Dynamic Indicator of Treatment Response in Children Receiving House Dust...

Clinical response to house dust mite subcutaneous immunotherapy (HDM-SCIT) in children is heterogeneous. Existing prediction approaches rely mainly on baseline characteristics and do not capture early treatment-related change.

Two ordinal regression models were developed. The base model included age, sex, baseline inhaled corticosteroid (ICS) dose (ICS₀), FEV₁ baseline, eosinophils, FeNOcat25, tIgE baseline, HDM_max, and ratio_max. The extended model additionally included early ICS change at 3 months (ΔICS), scaled per 100 μg/day (ΔICS_100). Model performance was assessed using Akaike information criterion (AIC), discrimination across four classification tasks, and calibration. Restricted cubic spline (RCS) analysis was used to examine the association between ΔICS and high response probability.

A total of 470 children were included, including 159 high responders, 151 middle responders, and 160 low responders. Adding ΔICS_100 significantly improved model fit (AIC 762.5 ± 3.3 vs. 871.2 ± 4.1; pooled Wald test, p < 0.001). The extended model showed better discrimination for high versus non-high response (area under the receiver operating characteristic curve 0.738-0.878), middle versus non-middle response (0.613-0.725), low versus non-low response (0.820-0.842), and high versus low response (0.856-0.928). RCS analysis demonstrated a significant nonlinear association between ΔICS and high response probability (overall p < 0.001; nonlinearity p < 0.001), with an inflection region around -80 to -50 μg/day.

Early change in ICS use (ΔICS) may provide additional predictive information beyond baseline variables in children receiving HDM-SCIT. The observed nonlinear association suggests that ΔICS may be a useful exploratory early treatment-related indicator, but external validation is required before clinical application.