β-d-Glucan and Aspergillus Galactomannan assays in the diagnosis of invasive fungal infections.

Author: 

Kumar M, Mugunthan M.
Med J Armed Forces India. 2019 Oct;75(4):357-360.

Abstract: 

BACKGROUND:

With an increase in the number of patients who are immunosuppressed or immunocompromised there has been an increase in invasive fungal infection (IFI) in the past few decades with its associated high morbidity and mortality, ranging from 60% to 90%. The critical problem is the identification of the causative fungus and initiation of appropriate therapy. Hence, there is a requirement for better diagnostic methods for IFI. Detection of markers for the presence of fungi during early stage of the infection, such as constituents of the cell wall or fungal DNA, is essential for timely diagnosis of IFI. Galactomannan (GM) which is a cell wall surface antigen is the most studied diagnostic marker, followed by 1,3 β-d-Glucan (BG) which is seen in deep layers of cell wall.

METHODS:

We have assessed the effectiveness of Galactomannan/β-d-Glucan for the early diagnosis of IFI in immunosuppressed patients in our tertiary care setting.

RESULTS:

The sensitivity, specificity, positive predictive value and negative predictive value of GM assay were 45%, 93%, 86% and 63% respectively, while the BG assay showed a sensitivity of 78%, specificity of 85%, Positive predictive value (PPV) 84% and Negative predictive value (NPV) 79%.

CONCLUSION:

BG assay is better for detection of IFI in patients with immunosuppression. However, a combination of both BG and GM assays would be the best approach as BG assay is highly sensitive, while the GM assay is highly specific for diagnosing IFI.