Although the clinical outcome in patients with Invasive Aspergillosis (IA) is largely dependent on early initiation of effective treatment with antifungal drugs, diagnosing IA is still a critical problem. Symptoms are non-specific and available diagnostic tools are either invasive or have low sensitivity and specificity. This often results in a diagnostic delay, with patients developing more extensive disease. Furthermore, as long as IA is present, oncological follow-up treatment is not feasible. Inaccuracy in diagnosing IA can cause serious treatment delay and increased mortality. However, an empirical strategy with prophylactic anti-mould therapy is not feasible considering both possible side effects and costs. In order to safely continue the use of a pre-empirical strategy, improved (non-invasive) diagnostic tools are desirable.