Evaluation of galactomannan and beta-d-glucan assays for the diagnosis of invasive aspergillosis in clinically suspected cases.

Abstract

To assess the utility of galactomannan and beta-D-glucan assays in the diagnosis of invasive aspergillosis in clinically suspected cases, and to compare their diagnostic potential to determine whether a combination of the two may result in an early and specific diagnosis. The descriptive cross-sectional case-control study was conducted at the Armed Forces Institute of Pathology, Rawalpindi, Pakistan, from April 1, 2017, to March 31, 2018, and comprised serum samples from clinically suspected invasive aspergillosis patients and healthy controls. The sera were tested for galactomannan and beta-D-glucan detection. Proven, probable and possible categories of invasive aspergillosis according to European Organisation for Research and Treatment of Cancer / Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group criteria. Galactomannan antigen was detected using a one-stage immunoenzymatic sandwich microplate assay. Beta-D-Glucan antigen was detected using a protease zymogen-based colorimetric assay. Sensitivity and positive / negative likelihood ratio of both the cases and the controls were calculated and compared. Of the 178 subjects, 119(67%) were cases and 59(33%) were controls. Beta-D-glucan assay was more sensitive than galactomannan assay (91.6% versus 80.67%) whereas galactomannan assay was more specific than beta-D-glucan assay (86.44% versus 76.27%) in the diagnosis of invasive aspergillosis. The sensitivities of both assays decreased with decreasing probability of invasive aspergillosis, i.e., maximum sensitivities of both beta-D-glucan and galactomannan assays were for proven cases (100% versus 87.5%), followed by probable cases (89.29% versus 85.71%), and possible cases (91.57% versus 78.31%). Both beta-D-glucan and galactomannan assays seemed to play an encouraging role in the diagnosis of invasive aspergillosis in high-risk clinically suspected cases, with the former assay being more sensitive and the latter assay being more specific.