Diagnosing Aspergillosis with Blood Tests

Galactomannan (GM) Testing

The American Thoracic Society recommends serum galactomannan testing for diagnosing invasive aspergillosis in patients with severe immunocompromise, with a strong recommendation and high-quality evidence 1, 2
Serum galactomannan testing is recommended for diagnosing invasive aspergillosis in patients with neutropenia, hematological malignancy, or recipients of hematopoietic stem cell or solid organ transplants, with a strong recommendation and high-quality evidence 1, 2
For optimal accuracy, two consecutive samples with an optical density index (ODI) ≥0.5 or retesting of the same sample is recommended 2, 3
Prospective monitoring should be performed every 3-4 days in high-risk patients and combined with HRCT and clinical evaluation 2, 3

BAL fluid GM testing is strongly recommended when serum GM is negative but clinical suspicion remains high, or when serum GM is positive but there are confounding factors for false-positive results 1, 2
BAL GM testing has excellent performance with optimal cut-off values between 0.5 and 1.0 2, 5

The Infectious Diseases Society of America recommends serum (1→3)-β-D-Glucan (BDG) testing for diagnosing invasive fungal infections, including aspergillosis, in high-risk patients 1, 6
BDG has limited specificity for Aspergillus as it is present in many fungal species 2, 6
Aspergillus PCR on blood samples shows variable performance with sensitivity of 88% and specificity of 75% for a single positive test 8
Combined use of PCR with GM testing provides greater diagnostic accuracy 8

Initial screening in high-risk patients should include serum GM testing every 3-4 days in neutropenic patients or hematopoietic stem cell transplant recipients 2, 3
If clinical suspicion persists despite negative serum tests, perform bronchoscopy with BAL for GM testing and culture 1, 2
For monitoring treatment response, serial serum GM testing is recommended, with decreasing values during the first 2 weeks indicating a favorable response 2, 4