Aspergillus galactomannan antigen assay in bronchoalveolar lavage fluid for diagnosis of invasive pulmonary aspergillosis.

OBJECTIVES

A recently developed bronchoalveolar lavage (BAL) galactomannan (GM) assay shows promising results. We evaluated the diagnostic performance of this assay and analyzed risk factors for false-positive results.

METHODS

A prospective cohort study was performed in a tertiary hospital over a 9-month period. We reviewed all adult patients who underwent GM assays of BAL. Patients were categorized with proven, probable, or possible invasive pulmonary aspergillosis (IPA) according to revised EORTC/MSG definitions. Each patient with a false-positive BAL GM result was matched with three patients with true-negative BAL GM result, and the risk factors for false-positive BAL GM results were determined.

RESULTS

Of 359 enrolled patients, 22 (6%) were diagnosed with IPA (1 proven, 17 probable, and 4 possible). Of the 22 patients with IPA, 17 (77%) had already received antifungal agents before the BAL GM assay was conducted. At an index cutoff value of ≥0.5, the BAL GM assay had a sensitivity of 64% (95% CI 41%-83%) and a specificity of 89% (95% CI 85%-92%). However, at an index cutoff value of ≥0.2, the BAL GM assay had a sensitivity of 86% (95% CI 65%-97%) and a specificity of 74% (95% CI 69%-79%). Of the 52 patients with positive BAL GM assay (≥0.5), 25 (7%) were false-positives. Univariate and multivariate analysis revealed that treatment with piperacillin-tazobactam or ampicillin-sulbactam was associated with false-positive BAL GM results.

CONCLUSIONS

The BAL GM assay appears promising for the diagnosis of IPA. However, treatment with certain antibiotics may interfere with the results of the BAL GM assay.