The early diagnosis of invasive aspergillosis is very important in order to treat patients in a stage of disease in which the fungal burden is low. Since culture is relatively insensitive in most patient groups, alternative methods have been explored. The evaluation of these new methods should focus on the performance characteristics of the assays as well as the point of disease at which the first positive result is obtained. Most promising microbiological methods include the detection of fungal DNA by PCR and detection of circulating antigens. The detection of a circulating Aspergillus antigen, galactomannan (GM), is now standardized thanks to the availability of a commercial kit, outside the USA. GM is released by all pathogenic Aspergillus species during growth and circulating GM can be detected in patients with invasive aspergillosis. The sensitivity of the ELISA is 55 to 100% and the specificity 80 to 100% depending on host group and study design. Several large prospective studies show that circulating antigen can be detected before a clinical diagnosis is made in over 60% of patients. Furthermore, the course of the antigen titer corresponds with the clinical response to disease in most patients. A drawback of the ELISA is that only Aspergillus species can be detected and speciation is not possible. False negative ELISA results have been reported in patients with Aspergillus abscesses. Furthermore, the majority of clinical studies have been performed with patients with hematological malignancies and evaluation in other risk groups is warranted.The detection of GM appears to be helpful to diagnosing invasive aspergillosis early, but the results should be used together with clinical findings, imaging techniques and culture. In addition, further studies are needed to gain insight in the kinetics of the markers and the effect of host response. Finally, new diagnostic techniques need to be incorporated in the current diagnostic strategies.
Full conference title:
- ICAAC 41st