The Effect Analysis of Different Experimental Methods for the Diagnosis of Invasive Pulmonary Aspergillosis in a Rat Model

Background: Consensus on the most reliable assays to detect invasive aspergillosis from minimally or noninvasive samples has not been reached. In this study, we compared the efficacy of an enzyme-linked immunosorbent assay (ELISA) for galactomannan (GM) detection and quantitative real-time PCR assay (qRT-PCR) for the diagnosis of invasive pulmonary aspergillosis in a rat model. Methods: Neutropenic, male Sprague-Dawley rats (specific pathogen free; 8 weeks old; weight, 200 ± 20 g) were immunosuppressed with cyclophosphamide and infected with Aspergillus fumigatus intratracheally. Tissue and whole blood samples were harvested on days 1, 3, 5, and 7 post-infection and examined with GM ELISA and qRT-PCR. Results: On day 7, A. fumigatus DNA was amplified from 14 of 48 whole blood samples from immunosuppressed infected rats: day 1 (0/12), day 3 (0/12), day 5 (6/12), day 7 (8/12) post infection. The sensitivity and specificity of the qRT-PCR assay were 29.2% and 100%, respectively. Receiver operating characteristic curve (ROC) analysis indicated a Ct cut-off value of 15.35, and the area under the curve (AUC) was 0.627. The GM assay detected antigen in sera obtained on day 1 (5/12), day 3 (9/12), day 5 (12/12), and day 7 (12/12) post-infection, and thus had a sensitivity of 79.2% and a specificity of 100%. The ROC of the GM assay indicated that the optimal cut-off value was 1.40 (specificity, 100%; AUC, 0.919). Conclusions: The GM assay was more sensitive than qRT-PCR assay in diagnosing invasive pulmonary aspergillosis in rats.