False-positive Aspergillus galactomannan assay in solid organ transplant recipients with histoplasmosis

False-positive Aspergillus galactomannan assay in solid organ transplant recipients with histoplasmosis:

Abstract:

Post-transplantation histoplasmosis may be acquired via inhalation, may result from endogenous reactivation, or may be derived from the allograft. The Histoplasma and Aspergillus enzyme-linked immunoassays are increasingly being relied upon for rapid diagnosis of fungal infections, especially in immunocompromised patients. We describe 4 cases of solid organ transplant recipients who had histoplasmosis and a falsely positive Aspergillus galactomannan (GM) obtained from the serum or bronchoalveolar lavage (BAL) fluid.
We also report our experience, testing for Histoplasma antigen (Ag) in specimens positive for AspergillusGM. From January 2007 through December 2010, of 2432 unique patients who had positive AspergillusGM tests, 514 (21%) were tested for HistoplasmaAg, and 27 were found to be positive. Most specimens that tested positive for both Aspergillus and Histoplasma were obtained by BAL. False-positive tests for AspergillusGM can occur in immunosuppressed patients who have histoplasmosis, and may obscure the correct diagnosis.