Session: Slide Session: From the Clinical Mycology Laboratory
Sunday, October 26, 2008: 12:00 AM
Room: Room 207
Background: Current Aspergillus detection methods are based upon the isolation of Aspergillus DNA from fungal cells in tissue (including white blood cells) or as unbound Aspergillus DNA in serum. We hypothesize that the combined use of two extraction methods to include all forms of circulating Aspergillus DNA as a PCR template will allow for the earlier diagnosis of IA. Methods: A total of 102 patients at high risk for IA were screened by PCR twice weekly and 16 patients with proven (5) or probable (11) IA were identified. For these 16 patients DNA was extracted from 365 serum (S) and 365 whole blood (WB) specimens. All serum only (SO), whole blood only (WBO) and the combination of (S+WB) extracts were tested using a nested PCR assay. Additionally, the 365 (S) specimens were tested by galactomannan (GM) ELISA. Results: Positive PCR results occurred with (S +WB) a median of 12 days before (WBO) and a median of 7 days before (SO) in 8 of 16 and 1of 16 patients with proven or probable IA respectively. In 6 of the 9 patients in whom (S+WB) was the first to be positive by PCR a concomitant increase in GM-ELISA titres was detected. Two patients who were neutropenic and also had proven IA of the sinuses were PCR positive with (SO) before (S+WB) and (WBO) became PCR positive. Conclusions: Combining Aspergillus DNA extracted from (S) and (WB) appears to make an earlier diagnosis of IA. This may be due to the ability to detect lower levels of Aspergillus DNA. The combination of (S) and (WB) specimens as a PCR template may be of use in detecting IA in patients on mould-active prophylaxis. GM ELISA results may be useful in the interpretation of (S+WB) PCR results to confirm the diagnosis of IA. Factors such as site of IA and neutropenia may influence the release of biomarkers and the choice of specimen used to diagnose IA.