Background ABPA may complicate asthma in some patients. The potential global ABPA burden remains unknown, limiting its prioritisation for both population and clinical responses.

Methods We estimated the number of adults with asthma, using the GINA statistics as the baseline dataset and this derived equation: Adult Prevalence (AP) = total prevalence × adult population/(0.88 paediatric population + adult population). This method provided results which were compatible with more direct sources on Scotland (Ananadan, 2010), North Africa (Nafti, 2009) and the USA (CDC stats, 2008). Two period prevalence rates available on ABPA in asthmatic patients are 0.72% (Ireland; Donnelly, 1991) and 3.5% (New Zealand; Eaton, 2000) (eliminating the non-classical cases from both papers) so we used a mean of 2.1% (range 0.72–3.5%). We estimated case burdens by WHO region and for the UK and USA.

Results By WHO region, the ABPA burden estimates are: Europe, 466 891 (range 160 077–778 152); Americas, 704 926 (range 241 689–1 174 877); Eastern Mediterranean, 187 963 (range 64 444–313 272); Africa, 294 058 (range 100 820–490 097); Western Pacific, 881 860 (range 302 352–1 469 766); South East Asia, 614 353 (range 210 635–1 023 922); and global, 3 150 052 (range 1 080 018–5 250 086) cases. The UK adult asthma and ABPA burdens are estimated to be 7.1M and 149 901 (range 51 395–249 835) cases, respectively, with those for the US being 24.5M and 515 787 (range 176 841–859 645) cases.

Conclusions ABPA is probably more common globally than has been appreciated. A lack of sufficient population research using current fungal diagnostic approaches and clinical research on antifungal therapy effects on the course of ABPA among different populations, limits our estimates' utility.