The study included 530 patients, with 7% of those identified as having ABPA sans asthma. This is the largest known investigation of the disease to date. However, as the research was conducted retrospectively at a specialist centre, and ABPA sans asthma is a difficult condition to diagnose, the true number of those affected is unknown.
Certain similarities were found between the two disease types. There were similar rates of coughing up blood (haemoptysis) and coughing up mucus plugs. Bronchiectasis, a condition where the airways are widened and inflamed, was found more often in those without asthma (97.3% vs 83.2%). However, the extent to which the lung was affected by bronchiectasis was similar in both groups.
Lung function tests (spirometry) were significantly better in those without asthma: normal spirometry was found in 53.1% of those without asthma, in comparison to 27.7% of those with asthma. Furthermore, ABPA sans asthma patients were significantly less likely to experience ABPA exacerbations.
To sum up, this study found that those experiencing ABPA sans asthma were likely to have better lung function and fewer exacerbations than those with ABPA and asthma. However, clinical symptoms, such as mucus pugs and haemoptysis occurred at similar rates and bronchiectasis was more common in ABPA sans asthma patients. This was the largest study to date on this subset of ABPA; however, further research is required to understand the condition better.
Full paper: Muthu et al. (2019), Allergic bronchopulmonary aspergillosis (ABPA) sans asthma: A distinct subset of ABPA with a lesser risk of exacerbation