Background IgE sensitisation to Aspergillus fumigatus is seen in a significant proportion of patients with refractory asthma. The EVITA3 study recently showed that three months’ treatment with voriconazole did not improve asthma-related outcomes in this patient group. It is not known whether daily variations in outdoor fungal spore levels are associated with concomitant fluctuations in symptoms and lung function in patients with Aspergillus-associated asthma.
Methods Participants in the EVITA3 study kept daily diaries of peak expiratory flow (PEF) and asthma symptoms during their follow-up period. These diary records were retrospectively analysed together with contemporaneous fungal spore levels measured locally, in those patients (n = 36) who consented to the secondary use of their clinical and research data. Participants also underwent skin-prick tests for Aspergillus, Alternaria, Cladosporium, Penicillium and Botrytis. For each participant, cross-correlation was used to investigate the relationship between PEF and local spore counts of Aspergillus/Penicillium, Alternaria, Cladosporium, Botrytis, Sporobolomyces, Tilletiopsis, and Didymella. Group-level relationships were investigated using linear mixed models for PEF and generalised estimating equations for daily symptom scores, with participants stratified by skin prick test status. The analyses were performed with the exposure and outcome measured on the same day (lag 0), and with the exposure lagged by 1 day with respect to the outcome (lag 1).
Results The analysis cohort comprised 20 men and 16 women with a mean (standard deviation) age of 60 (8) years. No significant or consistent relationships were observed between fungal spore counts and either PEF or self-reported symptom scores, regardless of skin prick test status and lag time between exposure and outcome. In a linear mixed model, the effect size of total fungal spore count on morning PEF was negligible (−0.000011, p = 0.343 for lag 0; −0.000002, p = 0.847 for lag 1).
Conclusion In this retrospective analysis we found no evidence of a significant link between fungal spore counts and either PEF or symptoms in patients with Aspergillus-associated asthma. Further research is required to confirm this result in a prospective study and to identify whether aeroallergen levels relate to other important asthma outcomes such as exacerbations.