Is There an Overlap in Immune Response Between Allergic Bronchopulmonary and Chronic Pulmonary Aspergillosis?

Background: Chronic pulmonary aspergillosis (CPA) and allergic bronchopulmonary aspergillosis (ABPA) are presumed to represent 2 distinct manifestations of Aspergillus species in the lung.

Objective: To investigate any possible overlap of the immunological tests used for diagnosing ABPA in proven cases of CPA.

Methods: In consecutive subjects with CPA, we calculated the proportion of subjects who tested positive for all the immunological investigations used to diagnose ABPA (Aspergillus fumigatus specific IgE >0.35 kUA/L, total IgE ≥500 IU/mL, and eosinophil count ≥500 cells/μL) or obligatory criteria (A. fumigatus specific IgE >0.35 kUA/L and total IgE ≥500 IU/mL).

Results: A total of 269 subjects (53.5% males) of CPA with the mean (standard deviation [SD]) age of 44.3 (14.7) years were enrolled. The most common underlying disease was previously treated pulmonary tuberculosis (n = 230, 85.5%). Ninety-three (34.6%) subjects had total IgE ≥500 IU/mL, whereas A. fumigatus specific IgE >0.35 kUA/L was seen in 112 (41.6%) subjects. Thirteen (4.8%) subjects met all the immunological criteria for ABPA, whereas 59 (21.9%) subjects met the obligatory criteria. Subjects meeting the obligatory criteria had significantly higher eosinophil count (P ≤ .0001), greater immediate cutaneous reactivity to Aspergillus antigen (CPA-others vs obligatory criteria, 9.8 ± 13.9 vs 13.9 ± 14.9 mm, P value = .048), higher A. fumigatus specific IgG (99.3 ± 61.9 vs 122 ± 66.6 mgA/L, P = .015), and greater number of fungal balls (0.9 ± 0.7 [range, 0-3] vs 1.1 ± 0.9 [range, 0-4], P = .026) compared with those without.

Conclusions: Approximately 5% of subjects with CPA fulfilled all the immunological criteria used for diagnosing ABPA, whereas 22% met the obligatory criteria for ABPA. Whether these patients would require a different management protocol requires further investigation.