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Objectives: Fungitell Assay (FA) is the most widely used test for determining serum beta-D- glucan (BDG) levels in Europe. However, the disadvantage of this test is the need for samples' to collect appropriate number of samples assuring optimal test usability. It poses a problem in laboratories with limited number of samples because of prolonged turnaorund-time and questionable impact on the diagnostic process and antifungal treatment of invasive fungal infections (IFI). Wako β-Glucan Test (WBG), recently launched in Europe, offers the possibility of individual sample testing. The objective of this study was to compare serum beta-D-glucan levels obtained by these two assays in patients with suspected IFI. Methods: The study was performed at the University Hospital Centre Zagreb, Department of Clinical and Molecular Microbiology. The Fungitell Assay (Associates of Cape Cod Inc.) and Wako β-Glucan Test (FUJIFILM Wako Chemicals Europe Gmbh) were performed on patients' sera and the results were interpreted according to manufacturers' instructions. Two to three serum samples were tested in each patient on two or three consecutive days. Discrepant results between two tests were explained and commented in the context of patients' clinical data. Results: Forty-four serum samples in 24 patients were tested. FA was positive in 13 and WBG in 9 patients. The results obtained with two different tests regarding positivity and negativity were correspondent in 83, 3% (20/24) of patients. In 16, 7% (4/24) of patients, the results were discordant, with positive FA and negative WBG result. Results for four patients with discordant FA and WBG results are shown in Table 1. When cut- off value for WBG was lowered from manufacturer's cut-off value of 11 pg/mL to 3, 8 pg/mL, as suggested in a recent publication, all the results, except one result in Patient 1, were concordant. Moreover, in Patient 1 diagnosis of IFI was excluded after diagnostic work-up as well as in Patient 2. In Patient 3, with a recent heart transplant, chest HR-CT was done eight days after last serum sample tested with both tests, demonstrated pulmonary infiltrates suspected by radiologist to be of fungal etiology and subsequently determined levels of BDG with FA only showed further increase. Aspergillus fumigatus grew in a culture of sputum and patient was treated with voriconazole. Patient 4 had a cystic fibrosis with A. fumigatus isolated in sputum and treated with voriconazole. In Patients 1, 2, and 4 the highest level of BDG determined with WBG was 5, 1 pg/mL, while in a Patient 3 the highest level was 9.62. Conclusion: In our study FA was more frequently positive in comparison to WBG test. Among patients with positive FA and negative WBG was a also a patient with IFI. This is in concordance with so far conducted studies showing superior sensitivity of FA. Therefore, cut-off value for WBG should be reconsidered. As the results of any of these tests should be evaluated in the context of clinical picture and microbiological and radiological findings, WBG test remains a useful alternative for laboratories with low number of samples. |
