A decision tree analysis to evaluate the optimal approach to screen allergic bronchopulmonary aspergillosis in asthmatic patients

Background: Various methods are available to screen for allergic bronchopulmonary aspergillosis (ABPA) in asthma, but their comparative performance remains uncertain.

Objectives: To identify the optimal screening algorithm for ABPA in asthmatic patients and evaluate the crude cost of various diagnostic approaches.

Methods: We performed a post hoc analysis of prospectively collected data from consecutive adult asthmatic patients evaluated for ABPA. The diagnosis was based on the revised International Society for Human and Animal Mycology ABPA Working Group criteria. Initial evaluations included measurements of serum Aspergillus fumigatus-IgE (≥0.35 kUA/L), serum total IgE (≥500 IU/mL), serum A. fumigatus-IgG (≥27 mgA/L), blood eosinophil count (BEC ≥500 cells/μL), and chest CT findings. A decision tree was manually constructed using recursive partitioning to identify the most effective diagnostic pathway.

Results: Among 543 adult asthmatics, 106 were diagnosed with ABPA. Serum A. fumigatus-IgE was positive in 221 (40.7%) patients, while serum total IgE was elevated (≥500 IU/mL) in 300 (55.3%) patients. The serum total IgE-based approach required 196 additional tests during screening, compared to 115 in the A. fumigatus-IgE method. The BEC-based strategy missed 28 cases of ABPA. Although the CT-directed protocol had the fewest false positives, it required 437 additional screening radiographic procedures and missed eight ABPA cases. The A. fumigatus-IgE pathway emerged as the most cost-effective, whereas imaging-based strategies were the most expensive.

Conclusions: Serum A. fumigatus-IgE is the optimal screening test for ABPA in asthma. It minimizes unnecessary testing while maintaining high diagnostic accuracy, making it a preferable approach in clinical practice.