Allergic bronchopulmonary Aspergillosis (ABPA) is a pulmonary hypersensitivity disease mediated by an allergic response to Aspergillus fumigates. ABPA occurs in, 10% of cystic fibrosis (CF) patients and may lead to acute worsening of respiratory status and ongoing decline in lung function, ultimately progressing to a chronic state and lung fibrosis without adequate treatment. Despite the existence of the gold-standard Nelson criteria, diagnosis of ABPA in CF patients remains difficult. The wide variation in diagnostic practices between clinics, different estimates of prevalence and a delay in recognition lead to under treatment (Virnig and Bush 2007).