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Published on: March 22, 2012
False-positive Aspergillus galactomannan assay in solid organ transplant recipients with histoplasmosis
P Vergidis1, R C Walker, D R Kaul
1Department of Medicine and William J. von Liebig Transplant Center, Mayo Clinic, Rochester, MN 55905, USA. vergidis.paschalis@mayo.edu
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 Aspergillus GM. From January 2007 through December 2010, of 2432 unique patients who had positive Aspergillus GM tests, 514 (21%) were tested for Histoplasma Ag, 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 Aspergillus GM can occur in immunosuppressed patients who have histoplasmosis, and may obscure the correct diagnosis.
Insights
Fungal infections in transplant patients can be misdiagnosed. False positives for Aspergillus galactomannan (GM) occur in histoplasmosis cases, potentially delaying correct treatment.
Area of Science:
- Mycology
- Transplant Infectious Diseases
- Clinical Diagnostics
Background:
- Post-transplantation fungal infections, including histoplasmosis, pose significant risks to immunocompromised patients.
- Rapid diagnostic tests like enzyme-linked immunoassays for Aspergillus and Histoplasma are crucial for timely management.
- Histoplasmosis in transplant recipients can arise from new infections, reactivation, or the allograft itself.
Observation:
- This study details four solid organ transplant recipients with histoplasmosis who exhibited false-positive Aspergillus galactomannan (GM) results.
- Aspergillus GM testing is widely used for diagnosing invasive aspergillosis in immunocompromised individuals.
- Bronchoalveolar lavage (BAL) fluid was the most common specimen yielding positive results for both Aspergillus GM and Histoplasma antigen.
Findings:
- Of 2432 patients with positive Aspergillus GM tests, 514 were tested for Histoplasma antigen, with 27 (5.3%) testing positive.
- False-positive Aspergillus GM results were observed in patients with confirmed histoplasmosis.
- Histoplasma antigen testing in specimens positive for Aspergillus GM identified co-infections or misdiagnoses.
Implications:
- False-positive Aspergillus GM tests in immunosuppressed patients with histoplasmosis can obscure the true diagnosis.
- Accurate differentiation between Aspergillus and Histoplasma infections is critical for appropriate antifungal therapy in transplant recipients.
- Implementing concurrent or sequential testing for Histoplasma antigen in cases of suspected fungal infection with positive Aspergillus GM can improve diagnostic accuracy.
