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In most cases
of cryptococcosis, antigen concentration will exceed antibody
and be detected in latex agglutination tests. However, in most
cases and in some stages of the disease, antigen may not be present
in excess and tests to detect antibody may be necessary to make
a serological diagnosis. In Central Nervous System (CNS) cryptococcocis,
antigen excess is present and detectable by latex agglutination
in spinal fluid in the vast majority of the cases. During successful
antifungal therapy, it is not uncommon for antigen tests to become
negative and antibody tests to become positive with rising titers.
In non-CNS disease (e.g., pulmonary, osteolytic, etc.), antibody
tests may be the only means for making a serological diagnosis,
since tests for antigen may or may not be positive.
The YA-Crypto
Tube Agglutination System is based upon the principle that yeast
cells of weakly encapsulated Cryptococcus neoformans strains will
agglutinate with specimens containing antibodies against C. neoformans.
The system detects these antibodies when present and is both qualitative
and semi-quantitative. It is most effective for detecting the
antibodies of C. neoformans in the serum of patients with pulmonary
and extrapulmonary cryptococcosis (non-meningeal); however, the
spinal fluid of cryptococcal meningitis patients may also contain
detectable levels of antibody, especially during and following
successful therapy. |