Allergic Bronchopulmonary Aspergillosis in the Asthma Clinic: A Prospective Evaluation of CT in the Diagnostic Algorithm

Abstract

Allergic bronchopulmonary aspergillosis (ABPA) occurs in cases of atopic asthma and may result in important lung disease. Early diagnosis is essential as this disease is responsive to steroids. However, while asthma is common, ABPA is infrequently diagnosed. CT allows precision in the diagnosis of central bronchiectasis (which is virtually pathognomonic of ABPA) and may enable earlier diagnosis. A prospective evaluation of 255 patients with asthma for ABPA, using skin prick testing (SPT) for Aspergillus fumigatus (AF) as a screening tool and incorporating CT into the diagnostic algorithm. Asthma clinic, Green Lane Hospital, Auckland, New Zealand. Patients with asthma. ABPA was diagnosed using "essential" criteria (ie, asthma, SPT positivity to AF, elevated serum total IgE, elevated serum AF-specific IgE, and pulmonary infiltrates seen on chest radiography or central bronchiectasis seen on CT scan) and "minimal essential" criteria (ie, asthma, SPT positivity, and central bronchiectasis). Two hundred fifty-five consecutive patients with asthma who consented to SPT were studied: 218 of 255 patients (86.8%) were atopic; and 47 of 255 patients (21.6%) were AF-positive, of whom 35 accepted further evaluation including CT scanning. A secure diagnosis of ABPA, satisfying all essential criteria, was evident in 9 of 35 patients (25.7%), a proportion that increased to 13 of 35 patients (37.1%) by using the minimal essential diagnostic criteria. SPT positivity to AF was present in approximately 20% of patients in the asthma clinic. A diagnosis of ABPA is disclosed by CT in 25 to 40% of SPT-positive patients, depending on the selection of diagnostic criteria. These findings support the use of SPT as a screening tool in the asthma clinic and indicate that a routine CT scan is warranted in SPT-positive patients.