What is the appropriate diagnostic workup for suspected aspergillosis?

Diagnostic Workup for Suspected Aspergillosis

For suspected invasive pulmonary aspergillosis (IPA), obtain a chest CT scan immediately, perform bronchoscopy with bronchoalveolar lavage (BAL) for galactomannan testing and culture, and obtain serum galactomannan and β-D-glucan in high-risk patients (hematologic malignancy, HSCT recipients). 1

Imaging Studies

• Chest CT scan is mandatory whenever IPA is clinically suspected, regardless of chest radiograph findings 1
• Perform CT without contrast as routine practice 1
• Use contrast only when a nodule or mass is located close to a large vessel 1
• CT findings help establish the pretest probability and guide further invasive diagnostic procedures 1

Bronchoscopy and Specimen Collection

Bronchoscopy with BAL is strongly recommended for suspected IPA, as it provides the highest diagnostic yield [1, @16@]

• Use a standardized BAL procedure and send samples for:
  • Routine culture and cytology 1
  • Galactomannan (GM) testing 1
  • Microscopic examination with optical brighteners 2
  • Consider PCR testing as an adjunct 1

Important caveats:

• BAL may be contraindicated in patients with severe hypoxemia, active bleeding, or platelet transfusion-refractory thrombocytopenia 1
• BAL has low yield for peripheral nodular lesions—consider percutaneous or endobronchial lung biopsy instead 1
• Submit adequate tissue and fluid quantities for simultaneous histopathologic/cytologic examination and culture 1

Biomarker Testing

Galactomannan (GM) Testing

Serum and BAL galactomannan is the most validated biomarker for IA diagnosis in specific populations 1

When to use GM:

• Strongly recommended for adult and pediatric patients with hematologic malignancy or HSCT recipients 1
• BAL GM can be used even in patients receiving mold-active antifungal prophylaxis (unlike serum GM) 1

When NOT to use GM:

• Not recommended for routine blood screening in patients already on mold-active antifungal therapy or prophylaxis 1
• Not recommended for screening in solid organ transplant (SOT) recipients 1
• Not recommended for screening in chronic granulomatous disease (CGD) patients 1

β-D-Glucan Testing

• Serum (1→3)-β-D-glucan is recommended for diagnosing IA in high-risk patients (hematologic malignancy, allogeneic HSCT) 1
• Critical limitation: β-D-glucan is not specific for Aspergillus and can be positive with other fungal infections 1

PCR Testing

PCR testing remains controversial but can be used selectively 1, 3

• Blood or serum Aspergillus PCR is recommended in severely immunocompromised patients (hematologic malignancy, HSCT, solid organ transplant recipients) suspected of having IPA 3
• BAL PCR shows high specificity (mean 96.4%) and sensitivity (mean 90.2%) 3
• Use PCR carefully on a case-by-case basis, understanding the specific assay's performance characteristics 1
• Always interpret PCR results in conjunction with other diagnostic tests and clinical context 1
• The lack of standardized commercial assays limits routine clinical use 1

Microbiological Methods

Culture and Microscopy

Culture and microscopic examination remain essential despite their limitations 2

• Fungal elements (hyphae) in primarily sterile specimens prove infection regardless of culture results 2
• Microscopy should use optical brighteners 2
• Histopathology should employ Gomori's methenamine silver stain or Periodic acid-Schiff stain 2
• Laboratory results should be reported immediately to clinicians 2
• Species identification to complex level is strongly recommended for all clinically relevant Aspergillus isolates, especially when atypical growth or resistance is suspected 1

Patient Population-Specific Considerations

High-Risk Patients (Hematologic Malignancy, HSCT)

• Use serum GM, β-D-glucan, chest CT, and bronchoscopy with BAL GM 1
• Consider PCR as adjunctive testing 3

Solid Organ Transplant Recipients

• Do NOT use serum GM for screening 1
• Rely on chest CT, BAL with culture, microscopy, and BAL GM 1

Chronic Granulomatous Disease

• Do NOT use serum GM for screening 1
• Emphasize tissue diagnosis and culture 1

Common Pitfalls

• Antifungal treatment decreases GM sensitivity—obtain samples before initiating therapy when possible 2, 4
• Negative culture does not exclude aspergillosis—culture is insensitive and time-consuming 5
• Single negative biomarker test is insufficient—use multiple diagnostic modalities in combination 1
• Do not delay imaging—chest radiographs are inadequate; proceed directly to CT 1
• Peripheral lesions require different sampling—BAL has low yield; consider percutaneous biopsy 1