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Background: The galactomannan (GM) assay is an approved noninvasive test for detection of invasive aspergillosis (IA) that has been validated in adult patients with hematologic malignancies who are undergoing bone marrow transplantation. There have been few studies with this assay in pediatric patients, but early reports suggest that there may be differences in the performance such that false-positive GM tests in pediatric patients are more common than in adult patients., Methods: We performed a prospective study in pediatric hematopoietic stem cell transplant recipients with twice-weekly sampling for GM detection during the highest risk periods of neutropenia and graft-versus-host disease. We analyzed 826 serum samples from 64 patients, including 15 serum samples from one patient diagnosed with probable IA according to defined criteria., Results: Twenty of 811 samples tested positive on repeat testing (specificity, 97.5%; 95% CI: 96.2-98.4%) including samples from 8 of 63 patients without clinical evidence of IA according to study criteria (specificity, 87.3%; 95% CI: 76.9-93.4%). Eleven patients received piperacillin/tazobactam therapy, and 4 of the 11 patients had a positive assay result coinciding with the dates of piperacillin/tazobactam administration. When samples from these patients were excluded, specificity increased to 98.4% (95% CI: 97.2-99.1%) by sample and to 91.5% (95% CI: 81.6-96.3%) by patient., Conclusions: The GM assay holds promise for early, noninvasive diagnosis of IA in high-risk children and false-positive results were not common or unexplainable. This study supports further validation of this assay in a large-scale, pediatric-dedicated format.

Invasive aspergillosis (IA) is a frequent complication of blood or marrow transplantation. Previous studies have reported that the Aspergillus galactomannan enzyme immunoassay (GM EIA) may be a useful diagnostic tool for IA, but its sensitivity is variable. We examined the performance of the GM EIA in 986 serum samples from 67 patients. Results demonstrated that decreasing the index cutoff for positivity to 0.5 increased its sensitivity, with minimal loss of specificity. The low cutoff increased the duration of test positivity before diagnosis by clinical means. Sensitivity was highest in patients who did not receive preventative mold-active antifungals (87.5%). A rabbit model demonstrated that the level of circulating antigen correlated with the tissue fungus burden. A quantifiable response to antifungal therapy in clinical samples and the rabbit model supports the development of this assay for early diagnosis and therapeutic monitoring. The 0.5 cutoff may allow for better performance as an early diagnostic test.