Allergic Bronchopulmonary Aspergillosis
Allergic Bronchopulmonary aspergillosis (ABPA) is a pulmonary disorder of asthmatic patients and patients with cystic fibrosis arising from an allergic response to multiple antigens expressed by Aspergillus fumigatus (AF) colonizing the bronchial mucus.Symptoms usually appear during the third and fourth decades of life and range from acute, recurrent asthma exacerbation with wheeze, cough, and lung infiltrates to generalized systemic features of fever, anorexia, headache and malaise. Sputum production is characterized by solid chunks of green to beige colored plugs.
Diagnosis of ABPA is dependent on several laboratory tests. Demonstrating elevated levels of AF specific antibodies is considered the hallmark of disease. ELISA test is particularly useful in distinguishing asthmatic patients without ABPA from patients with ABPA. Asthmatic patients with ABPA have a 2 fold higher level of IgE AF specific antibodies in their serum.
The total IgE serum level is elevated to higher than 1000 ng/mL and often may reach levels >10,000. A normal level in a symptomatic patient can exclude the diagnosis of ABPA, especially if AF specific IgE is also normal.Total serum IgE level is an important tool to follow patients over time. The level fluctuates with exacerbations and remissions. It should fall to baseline when a patient is in remission.
A peripheral blood eosinophil count higher than 1 x 106/uL is a nonspecific marker of disease activity. The level may be suppressed in patients taking corticosteroids.
Culture of AF in the sputum is supportive but not diagnostic of ABPA. However, if sputum cultures are positive in patients with longstanding, refractory, corticosteroid dependent asthma, further immunologic testing to exclude the diagnosis of ABPA is required.
