Comparison of a novel lateral-flow device to galactomannan assay at different time periods for detections of invasive aspergillosis.

PURPOSE: To compare a lateral-flow device (LFD) method to the galactomannan assay (GM) for the diagnosis of invasive aspergillosis (IA).

METHODS

First, 20 GM-positive serum samples stored for two years were retested with both the GM and LFD assays. Second, 153 serum samples from 91 immunocompromised patients suspected of having IA were tested prospectively, including 56 hematologic malignancies and 35 chronic illnesses with steroid therapy.

RESULTS

For the twenty GM-positive stored samples, only ten were positive for the repeated GM assay and none were positive for IA according to the LFD test. The concordance of the LDF with the GM test was 79.81% (83/104) if both tests were performed on the sample collection day, with the rate reducing to 67.65% (23/34) (p < 0.05) if the LFD test was performed 2-7 days after the GM test. Furthermore, there was a significant difference in the discrepancy between the GM and LFD tests between previous and no anti-mold exposure subgroups (33.33% vs. 12.31%, p < 0.01). The sensitivity and specificity of the GM test were 89.65% and 98.66%, 68.96%, and 78.67% for the LFD assay.

CONCLUSION

Serum samples that have been stored long term are not suitable for re-testing with the GM or LFD assay. There was a strong correlation between the LFD and GM assay results if the tests were performed on the same day, however, this decreased if the samples were stored for more than 2 days. Additionally, previous exposure to antibiotics and/or antifungal therapy could influence the LFD results, leading to discrepancies with the GM test results.