What does a negative cryptococcal antigen mean?

Falsely negative results can occur in patient with high organism loads due to the high dose hook effect, which is also referred to as prozone. This occurs when excess analyte, such as high concentrations of the cryptococcal antigen, result in decreased visual intensity of the test lines and negative test results.

What could cause a false positive result when testing for cryptococcal antigen?

Fortunately, the causes of false-positive CAD tests are few. Likely the most noted cause is an infection and cross-reaction with a Trichosporon species (4, 5). Rarely, other causes, such as starch, disinfectants, and soap, have been reported to cause false-positive CAD results (1, 2, 6).

How do you test for cryptococcal antigen?

The test works by detecting cryptococcal antigen (abbreviated “CrAg”), an indicator of infection, in serum (a component of blood) and in cerebrospinal fluid (CSF). The antigen test can detect cryptococcal antigen in serum a median of 22 days before symptoms of meningitis develop.

What is Post zone effect?

The Post-zone Phenomenon is a false-negative test caused by excessive antigen, relative to antibodies, which prevents antibody-to-antigen crosslinking [4]. Crosslinking is necessary for immunochromatographic detection [4].

What does a positive cryptococcal antigen mean?

Interpretation. The presence of cryptococcal antigen in any body fluid (serum or cerebrospinal fluid) is indicative of cryptococcosis. Specimens that are positive by the lateral flow assay screen are automatically repeated with the same method utilizing dilutions in order to generate a titer value.

What is the zone of equivalence?

: the part of the range of possible proportions of interacting antibody and antigen in which neither or but small traces of both remain uncombined in the medium.

What are natural antibodies?

Natural antibodies (NAb) are defined as germline encoded immunoglobulins found in individuals without (known) prior antigenic experience. NAb bind exogenous (e.g., bacterial) and self-components and have been found in every vertebrate species tested. NAb likely act as a first-line immune defense against infections.

What are the symptoms of Cryptococcus?

The symptoms of cryptococcal meningitis include:

• Headache.
• Fever.
• Neck pain.
• Nausea and vomiting.
• Sensitivity to light.
• Confusion or changes in behavior.

What type of test will detect whole antigens?

Agglutination Testing Agglutination tests detect antibody or antigen and involve agglutination of bacteria, red cells, or antigen- or antibody-coated latex particles.

What happens when there is an excess of antibody against the antigen in a system?

When there is a large excess of antibodies, each antigen molecule is covered with antibody and removed by macrophages bearing receptors for the Fc component of the antibody molecules.