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1. What Is 1,3-β-D-Glucan (BDG)?

1,3-β-D-Glucan is a polysaccharide component of the fungal cell wall.
It is mainly detected in:

• Candida spp.
• Aspergillus spp.
• Pneumocystis jirovecii
• Most other pathogenic fungi

Note:

• Cryptococcus and Zygomycetes (Mucor, Rhizopus) have minimal β-D-Glucan → often not detected by this test.
• Blood BDG elevation suggests invasive fungal infection (IFI).

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2. Purpose of BDG Testing

• Early diagnosis of IFI
  • Can suggest infection even if blood cultures are negative
  • Useful in candidemia, invasive aspergillosis, PJP
• Monitoring immunocompromised patients
  • Hematopoietic stem cell transplant
  • Chemotherapy
  • Solid organ transplant
  • Long-term steroids or immunosuppressants
• Adjunctive monitoring of antifungal therapy

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3. Test Method — Colorimetric Assay

How It Works

1. Patient serum reacts with BDG reagent
2. Fungal cell wall component triggers a chemical color change
3. Optical measurement quantifies BDG levels

Specimen

• Serum (no anticoagulants)
• Antifungal therapy does not prevent testing

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4. Reference Ranges (Typical)

Result	Interpretation
< 60 pg/mL	Negative
60–79.9 pg/mL	Indeterminate / Borderline
≥ 80 pg/mL	Positive — suggests invasive fungal infection

Cut-off may vary depending on lab and assay kit.

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5. Clinical Significance

Positive (≥ 80 pg/mL)

• Invasive Candida infections
• Invasive Aspergillus infections
• Pneumocystis jirovecii pneumonia (PJP)
• Useful when respiratory specimens are difficult to obtain in immunocompromised patients

Borderline (60–79.9 pg/mL)

• Early infection or low fungal burden
• Reduced immune response may cause borderline values
• Requires additional diagnostics:
  • CT imaging
  • Blood cultures
  • Galactomannan
  • Other fungal markers

Negative (< 60 pg/mL)

• IFI less likely
• Does not rule out Cryptococcus or Mucor infections

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6. Interpretation Considerations

⚠️ 1) False Positives

BDG may elevate due to:

• Cellulose filters in hemodialysis
• Albumin or IVIG infusion
• Massive transfusions
• Certain β-lactam antibiotics
• Contaminated blood culture bottles
• Severe bacterial sepsis

→ Always interpret alongside clinical presentation, imaging, and other fungal markers.

⚠️ 2) Cryptococcus & Zygomycetes

• Rarely detected by BDG due to cell wall composition
• Alternative tests: Cryptococcal antigen, Mucor PCR

⚠️ 3) During Antifungal Therapy

• BDG may remain elevated days to weeks after therapy starts
• Single measurements should not solely guide treatment

⚠️ 4) BDG is Adjunctive

• Diagnosis requires clinical context plus:
  • Imaging (CT/MRI)
  • Blood cultures
  • Galactomannan or PCR
  • Histopathology when available

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7. Summary

Item	Key Points
Test Name	1,3-β-D-Glucan (BDG)
Method	Colorimetric Assay
Reference	< 60 Negative / ≥ 80 Positive
Clinical Use	Detects most invasive fungal infections (Candida, Aspergillus, PJP)
Limitations	False positives common; Cryptococcus/Mucor not detected
Specimen	Serum

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8. References

• Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 6th ed.
• Pappas PG et al. Clinical Practice Guideline for the Management of Candidiasis (IDSA)
• Koo S, Keil SD et al. β-D-Glucan Testing in Invasive Fungal Infections
• CLSI guidelines for fungal diagnostics
• Henry’s Clinical Diagnosis and Management by Laboratory Methods, 24th ed.