Abstract
BackgroundGalactomannan antigen (GM) testing is widely used in the diagnosis of invasive aspergillosis (IA). Digestive enzymes play an important role in enzyme substitution therapy in exocrine pancreatic insufficiency. As digestive enzymes of fungal origin like Nortase contain enzymes from Aspergillus, a false-positive result of the test might be possible because of cross-reacting antigens of the cell wall of the producing fungi. We, therefore, asked whether the administration of fungal enzymes is a relevant cause of false-positive GM antigen test results.MethodsPatients with a positive GM antigen test between January 2016 and April 2020 were included in the evaluation and divided into two groups: group 1—Nortase-therapy, group 2—no Nortase-therapy. In addition, dissolved Nortase samples were analyzed in vitro for GM and β-1,3-D-glucan. For statistical analysis, the chi-squared and Mann‒Whitney U tests were used.ResultsSixty-five patients were included in this evaluation (30 patients receiving Nortase and 35 patients not receiving Nortase). The overall false positivity rate of GM testing was 43.1%. Notably, false-positive results were detected significantly more often in the Nortase group (73.3%) than in the control group (17.1%, p < 0.001). While the positive predictive value of GM testing was 0.83 in the control group, there was a dramatic decline to 0.27 in the Nortase group. In vitro analysis proved that the Nortase enzyme preparation was highly positive for the fungal antigens GM and β-1,3-D-glucan.ConclusionsOur data demonstrate that the administration of digestive enzymes of fungal origin like Nortase leads to a significantly higher rate of false-positive GM test results compared to that in patients without digestive enzyme treatment.
Highlights
Invasive aspergillosis (IA) is a significant cause of morbidity and mortality in immunocompromised patients [1]
Since the sensitivity of Aspergillus culture or microscopy in blood and bronchoalveolar lavage (BAL) is often poor, Aspergillus antigen testing is recommended for patients who are at risk or suspicion of invasive aspergillosis (IA) [3,4,5]
The Galactomannan antigen (GM) test is a double-sandwich enzyme-linked immunosorbent assay (ELISA), which is widely used for testing serum and BAL fluid for IA
Summary
Invasive aspergillosis (IA) is a significant cause of morbidity and mortality in immunocompromised patients [1]. Galactomannan (GM) is a polysaccharide and a major constituent of cell walls of Aspergillus species It can be detected in the host’s bloodstream during invasive infection [6]. As digestive enzymes of fungal origin like Nortase contain enzymes from Aspergillus, a false-positive result of the test might be possible because of cross-reacting antigens of the cell wall of the producing fungi. We asked whether the administration of fungal enzymes is a relevant cause of false-positive GM antigen test results. In vitro analysis proved that the Nortase enzyme preparation was highly positive for the fungal antigens GM and β-1,3-D-glucan. Conclusions Our data demonstrate that the administration of digestive enzymes of fungal origin like Nortase leads to a significantly higher rate of false-positive GM test results compared to that in patients without digestive enzyme treatment
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