Assays for Invasive Fungal Disease

[Moldleg333]

This is to inform of different tests that are used. This test however
is not specific to what type of mold, fungi, or yeast is causing the
infection. Currently this test is only approved for use in transplant
patients. It is still an adjunct to prove that infection has occurred
as with IA of Candida.


Two new antigen-based tests show promise and could prove useful for
immunocompromised patients.
Early diagnosis and therapy is critical to the management of patients
with invasive fungal disease (IFD). Although diagnosis has been based
on culture or microscopy, antigen-based assays to detect (1 3)-β-D-
glucan (BG) and Aspergillus galactomannan recently became available.
Both rely on identification of polysaccharides associated with the
cell wall of fungal pathogens. Now, two research groups have examined
the performance and usefulness of these assays in patients at risk for
IFD.
Koo and colleagues retrospectively reviewed the results of 1308 serum
BG assays performed for 871 patients. For patients tested more than
once, the results of the first BG test were used. A BG level 80 pg/mL
had a sensitivity of 64% and a specificity of 84% for a diagnosis of
IFD within 1 week. Sensitivity was 71% and specificity was 81% for
such a diagnosis by the end of hospitalization. Albumin, intravenous
immunoglobulin, and hemodialysis independently increased BG levels.
When patients with these factors were excluded from analysis, the
specificity of the test increased slightly, but the sensitivity
remained unchanged.
Maertens and colleagues examined the use of the Platelia Aspergillus
galactomannan assay on bronchoalveolar lavage (BAL) fluid from
patients hospitalized for hematologic disorders. (One of the authors
has received support from the assay maker.) Among 99 BAL samples, the
mean optical density for the assay was 4.3 for 58 patients with proven
or probable invasive pulmonary aspergillosis (IPA) compared with 0.6
for 41 controls without this diagnosis. At an optical density 1.0,
sensitivity was 91% and specificity was 88% for diagnosing IPA. For
culture or microscopy, the sensitivity was only 74%.
Comment: These reports indicate the value of newer, antigen-based
techniques for diagnosing IFD. Because neither assay depends on host
immune response, both are useful for immunocompromised patients.
Although caveats remain regarding their interpretation, these tests
are important additions to our armamentarium.
-- Neil M. Ampel, MD
Published in Journal Watch Infectious Diseases November 18, 2009
Citation(s):
Maertens J et al. Bronchoalveolar lavage fluid galactomannan for the
diagnosis of invasive pulmonary aspergillosis in patients with
hematologic diseases. Clin Infect Dis 2009 Dec 1; 49:1688.
· Medline abstract (Free)
Koo S et al. Diagnostic performance of the (1 3)-β-D-glucan assay for
invasive fungal disease. Clin Infect Dis 2009 Dec 1; 49:1650.
· Medline abstract (Free)