What is the first step in evaluating ABPA in asthma patients?

The first step in evaluating allergic bronchopulmonary aspergillosis (ABPA) in asthma patients is to establish IgE sensitization to Aspergillus. This is crucial because ABPA is primarily an allergic reaction to the fungus Aspergillus, often Aspergillus fumigatus, in individuals who have asthma or cystic fibrosis.

Detecting specific IgE antibodies against Aspergillus not only confirms sensitization but also supports the diagnosis of ABPA. The presence of elevated total IgE levels and specific IgE to Aspergillus species is a hallmark of ABPA, thus directing management and intervention.

While other diagnostic tools such as chest X-rays, CT scans, and pulmonary function tests can provide additional information about the patient's respiratory status and the extent of disease, they do not address the primary concern of underlying fungal sensitization. Therefore, establishing IgE sensitization serves as the critical initial step in the diagnostic process for ABPA in patients with asthma.