Aspergillus is a fungus found in soil, on farms and on construction sites. In those whose immune system is impaired it causes severe infection. The people who are particularly at high-risk of infection with Aspergillus (which is called Invasive Aspergillosis)are those with acute leukaemia who are having chemotherapy and those post bone marrow transplantation. Currently 15% of those at high-risk develop Invasive Aspergillosis and 60-90% of those with Invasive Aspergillosis die.

The main reason for this high death rate is that our current diagnostic tests are not good at detecting infection or often only detect the infection at advanced stages when treatment is ineffective. Because of the limitations of current diagnostic tests the current practice is to give empiric antifungal therapy (EAFT) early to treat suspected Invasive Aspergillosis. However studies have demonstrated that this therapy has only resulted in a minor reduction in the mortality rates and it also causes significant drug toxicity. It is a suboptimal treatment modality.

New tests have recently been developed to diagnose Invasive Aspergillosis. These tests are for the detection of an Aspergillus protein in blood and for the detection of Aspergillus DNA in blood. Available data suggests that these new tests make an early diagnosis and seem to be able to monitor responses to treatment. However no study has been reported to date which demonstrates that the use of these tests can impact on important patient outcomes. This trial is being performed to determine whether the use of the new diagnostic tests to guide antifungal therapy will help improve treatment of Invasive Aspergillosis, reduce drug toxicity and reduce the death rate in the high-risk patients as compared with the current standard method of diagnosis and treatment with EAFT.