Abstract Background International consensus-definitions for invasive aspergillosis (IA) in research are rigorous, yet clinically-significant cases are often excluded from clinical studies for not meeting proven/probable IA case-definitions. To better understand reasons for the failure to meet criteria for proven/probable infection, we herein review 47 of such cases, for their clinical, microbiological characteristics and outcomes. Methods Data on 47 cases not meeting consensus IA definitions but were deemed significant were derived from a retrospective, observational, multicenter survey of 382 presumed IA cases across Australasia, of which findings of 221 proven/probable infections were recently published. Clinical, microbiological, radiological characteristics of these cases were analysed. Mortality outcomes were compared with those of 221 proven/probable cases. Results Of 47 cases studied, 15 lacked classical host-factors, 22 exhibited only single positive Aspergillus PCR result, 7 lacked typical IA radiological findings on chest computed tomography, 3 had borderline galactomannan optical density indices (<1.0 but ≥0.5) in bronchoalveolar lavage fluid. Median age of patients was 61 years (IQR 52-68); 34 were males (72%). Seven patients (15%) required intensive-care admission. All patients had lung as primary site of infection. Antifungal treatment was initiated in 42 patients (89%). All-cause 90-day mortality was 33%, similar to 30% mortality in the comparative cohort (n=221). Conclusion Our findings highlight the limitations of current consensus-definitions for IA. Notably, the mortality of patients not meeting these definitions was similar to those with proven/probable IA. Further studies, especially of patients with single positive Aspergillus PCR and those without host-factors, are needed to determine if future consensus-definitions may benefit from modifications.