Allergic bronchopulmonary aspergillosis in the asthma clinic - A prospective evaluation of CT in the diagnostic algorithm

Objective: Allergic bronchopulmonary aspergillosis (ABPA) occurs in cases o f atopic asthma and may result in important lung disease. Early diagnosis i s essential as this disease is responsive to steroids. However, while asthm a is common, ABPA is infrequently diagnosed. CT allows precision in the dia gnosis of central bronchiectasis (which is virtually pathognomonic of ABPA) and may enable earlier diagnosis. Design: A prospective evaluation of 255 patients with asthma for ABPA, usin g skill prick testing (SPT) for Aspergillus fumigatus (AF) as a screening t ool and incorporating CT into the diagnostic algorithm. Setting: Asthma clinic, Green Lane Hospital, Auckland, New Zealand. Participants: Patients with asthma. Interventions: ABPA was diagnosed using "essential" criteria (ie, asthma, S PT positivity to AF, elevated serum total IgE, elevated serum AF-specific I gE, and pulmonary infiltrates seen on chest radiography or central bronchie ctasis seen on CT scan) and "minimal essential" criteria tie, asthma, SPT p ositivity, and central bronchiectasis). Measurements and results: Two hundr ed fifty-five consecutive patients with asthma who consented to SPT were st udied: 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 s canning. 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, Conclusions: SPT positivity to AF was present in approximately 20% of patie nts in the asthma clinic. A diagnosis of ABPA is disclosed by CT in 25 to 4 0% of SPT-positive patients, depending on the selection of diagnostic crite ria. These findings support the use of SPT as a screening tool in the asthm a clinic and indicate that a routine CT scan is warranted in SPT-positive p atients.