Assessment of specific immunotherapy efficacy using a novel placebo score–based method

BACKGROUND: In trials of allergen immunotherapy, allergen exposure is typically assessed by pollen counts, but these may misrepresent exposure if performed remotely from multiple study centers. OBJECTIVE: To assess whether symptomatology in placebo-treated patients is a better measure of local allergen burden at individual centers in such trials. METHODS: Data from a multicenter, placebo-controlled trial of preseasonal grass pollen immunotherapy were reanalyzed to identify the 4 weeks at each center in which the placebo-treated subjects had the highest combined symptom/medication scores (CSMS). The difference in CSMS between active and placebo groups was compared during the 4 peak placebo score weeks (PlSW) and the 4 peak pollen count weeks (PoCW). RESULTS: The benefit of immunotherapy over placebo in the PlSW analysis (18.5%) was greater than in the PoCW analysis (13.6%), with increased statistical significance (P = .0001, .0038, respectively). Similar improved discrimination was observed when analyzing benefits in subgroups of patients with severe symptoms, a high disease burden, and in different geographical locations. CONCLUSION: This novel PlSW analysis results in better discrimination of the effects of allergen immunotherapy compared with placebo and may be widely applicable in similar studies, both prospectively and retrospectively.