We have read with great interest the article by Baxter et al1 in CHEST (May 2013) highlighting the importance of sensitization to Aspergillus fumigatus (Af) in progression of cystic fibrosis (CF) lung disease. We and many others have previously reported that sensitization to Af is frequent in patients with CF: It was observed in 31% of the patient cohort (n = 153) who were followed up at the Leuven CF referral center.2 We also confirmed significantly impaired lung function parameters in Af-sensitized compared with Af-nonsensitized patients, with an average difference in FEV1 of 19 ± 4% predicted. In a multivariate analysis with age, sex, BMI, Pseudomonas aeruginosa colonization, pancreatic insufficiency, and gastroesophageal reflux disease as covariates, a significantly lower FEV1 and vital capacity (P < .001) was associated with Af sensitization, as well as an increased airway resistance (P < .05) and hyperinflation (higher residual volume, P < .001) (e-Table 1). Interestingly, no significant differences in lung function parameters were found between patients with serologic criteria for allergic bronchopulmonary aspergillosis (ABPA) (n = 17) and patients with sensitization to Af without ABPA. Similar to the data presented by Baxter et al1 and others,3 we observed, in a 3-year period, more exacerbations in Af-sensitized patients with CF compared with patients without sensitization to Af (5.30 ± 4.54 vs 1.69 ± 2.78 hospital admissions for IV antibiotic therapy, respectively; P < .005).