The Composite Asthma Severity Index: A Tool for Assessing Impact of Omalizumab Treatment in Children with Moderate-to-Severe Persistent Allergic Asthma

RATIONALE: The Composite Asthma Severity Index (CASI) is a validated, multidimensional instrument for determining asthma severity using 5 domains: day symptoms and albuterol use, night symptoms and albuterol use, controller treatment, lung function, and exacerbations (Wildfire et al., JACI 2012). In this post hoc analysis from a randomized, controlled trial of omalizumab, CASI was examined as a tool for assessing impact of treatment intervention in children ≥6 to <12 years with moderate-to-severe persistent allergic asthma.

METHODS: Poisson regression analysis examined exacerbation rate reductions for omalizumab versus placebo at Week 24 stratified by median CASI score at baseline (≤7 (n=360) vs. >7 (n=216)). A higher CASI score indicates more severe asthma. Clinically significant exacerbations were defined as those requiring either systemic corticosteroid therapy or a doubling of baseline inhaled corticosteroid dose for ≥3 days.

RESULTS: Baseline age, sex, total IgE and eosinophil levels were similar between treatment groups and across CASI strata. The CASI>7 group had higher proportions of black children, males, lower mean percent predicted pre-bronchodilator FEV₁, and greater maximum reversibility than the CASI≤7 group. Exacerbation rates were reduced by the following for omalizumab versus placebo: CASI≤7, 20% (-16%, 44%; p=0.24); CASI>7, 45% (18%, 63%; p=0.004).

CONCLUSIONS: CASI is a useful clinical tool to identify children who are likely to achieve favorable response to omalizumab. In children with greater asthma severity, as measured by a higher CASI score, a significantly greater response to omalizumab was observed for exacerbation reduction versus placebo; children with lower CASI scores had nonsignificant differences in reductions in exacerbation rates.