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.