Prospects for the early diagnosis of invasive aspergillosis in the immunocompromised patient

In recent years there has been some progress in diagnosing invasive aspergillosis at an early stage of disease. Polymerase chain reaction (PCR) assays are more sensitive than culture for detecting Aspergillus sp in bronchoalveolar lavage (BAD fluid specimens but diagnostic reliability may be diminished by false-positive reactions when patients are colonized with Aspergillus conidia or by laboratory contamination. Aspergillus antigens can be detected with a rapid, commercially-available, latex-agglutination (LA) test which employs the monoclonal antibody EB-A2 raised against Aspergillus galactomannan. The sensitivity of this test was found to be 38–95%, and positive test results were obtained only during advanced stages of disease. Recently, a sandwich ELISA has been developed which employs the same monoclonal antibody but was almost 10 times more sensitive than the LA test. This ELISA test yielded a sensitivity of 90% when a series of serum samples was employed. Furthermore, Aspergillus galactomannan was detected in the serum at an earlier stage of infection than that detected by the LA test. The development of sensitive diagnostic methods such as these offers an opportunity for optimizing diagnosis and improving the management of invasive aspergillosis. By allowing selective targeting of patients for antifungal therapy to pre-empt invasive aspergillosis, the outlook for patients at risk should be improved in terms of both morbidity and mortality.