Week 5 - serum fungal markers

Question 1

What is galactomannan?

Answer 1

polysaccharide that makes up the cell wall of mold-like fungi (aspergillus, penicillium)

Question 2

What is the specificity of galactomannan ELISA testing?

Answer 2

88.8%

Question 3

What is the sensitivity of galactomannan ELISA testing?

Answer 3

79.3%

Question 4

What is the negative predictive value of a negative galactomannan assay?

Answer 4

> 97% in both adult and pediatric populations

Question 5

Which is more sensitive, galatomannan from BAL or serum?

Answer 5

BAL - 85% sensitive when BAL, 23% from same-day serum galactomannan

Question 6

Which has a higher positivity rate of galatomannan and why – bronch wash vs BAL?

Answer 6

Bronch wash has higher positivity, unclear clinical significance as hypothesis is that bronchial airways contain more aspergillus hyphage with more galactomannan release than alveoli, BAL could be more diluted

Question 7

What is the general spectrum of aspergillus lung disease?

Answer 7

1) Invasive pulmonary aspergillosis (rapid, fatal)
2) Allergic bronchopulmonary aspergillosis (ABPA, exaggerated immune response)
3) Aspergilloma (fungus ball, develops in preexisting cavities)
4) Chronic necrotizing pulmonary aspergillosis (indolent, cavitary, secondary infection from aspergillus invasion)

Question 8

What is the sensitivity of serum galactomannan in ABPA?

Answer 8

Poor, 25.7%. Role of testing is limited in ABPA

Question 9

What are factors of aspergillus galactomannan cross-reactivity?

Answer 9

Bacteria: Staph epidermidis, E faecalis, Corynebacterium jeikeium, E coli
Fungus: Cryptococcus, Penicillium, Geotrichum, Histoplasma, Candida
Antibiotics: pip-tazo and Augmentin when long duration

Question 10

What is beta-D glucan?

Answer 10

Component of cell walls of most fungi, exceptions are Mucorales and Cryptococci

Question 11

What is the sensitivity and specificity of BDG testing in invasive fungal infections

Answer 11

97% sensitive, 93% specific

NPV 97%, PPV 59%

Question 12

What factors can create BDG cross-reactivity, resulting in false positives?

Answer 12

• Abx: pip-tazo, Augmentin
• Human blood products: albumin, immunoglobulins
• HD with cellulose membrane
• Host: mucositis, high triglycerides, elevated Hgb, bacteremia (strep, pseudomonas, E coli)

Question 13

What is the spectrum of immunocompromised pts we should test for fungal infections

Answer 13

• Highest: hematologic cancers, neutropenic pts, s/p HSCT
• moderate: solid-organ transplant
• lowest: auto-immune dz, solid cancer, steroid therapy