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Interpretive Handbook

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Test 28072 :
Cryptococcus Antigen, Spinal Fluid

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Cryptococcosis is an invasive fungal infection caused by Cryptococcus neoformans. The organism has been isolated from several sites in nature, particularly weathered pigeon droppings.

 

Infection is usually acquired primarily via the pulmonary route. Patients are often unaware of any exposure history. Approximately half of the patients with symptomatic disease have a predisposing immunosuppressive condition such as AIDS, steroid therapy, lymphoma, or sarcoidosis. Symptoms may include fever, headache, dizziness, ataxia, somnolence, and cough

 

In addition to the lungs, cryptococcal infections frequently involve the central nervous system (CNS), particularly in patients infected with HIV. Mortality in CNS cryptococcosis may approach 25% despite antibiotic therapy. Untreated CNS cryptococcosis is invariably fatal. Disseminated disease may affect any organ system and usually occurs in immunosuppressed individuals.

 

Note: According to the College of American Pathologists (CAP, IMM.41840), cerebrospinal fluid (CSF) specimens submitted for initial diagnosis that test positive by the latex agglutination assay should also be submitted for routine fungal culture. Fungal cultures are not required for CSF specimens that are submitted to monitor Cryptococcus antigen titers during treatment.

Useful For Suggests clinical disorders or settings where the test may be helpful

Aiding in the diagnosis of cryptococcosis

Interpretation Provides information to assist in interpretation of the test results

The presence of cryptococcal antigen in any body fluid (serum or cerebrospinal fluid: CSF) is indicative of cryptococcosis.

 

Ninety-five percent of cryptococcal meningitis cases exhibit positive latex agglutination in the CSF.

 

Higher titers appear to correlate with more severe infections. Declining titers may indicate regression of infection. However, monitoring titers to cryptococcal antigen should not be used as a test of cure, as low-level titers may persist for extended periods of time following appropriate therapy and the resolution of infection as measured by smear and culture.

 

CSF specimens that test positive by the latex agglutination assay should also be submitted for routine fungal culture. Culture can aid to differentiate between the 2 common Cryptococcus species causing disease (Cryptococcus neoformans and Cryptococcus gattii) and can be used for antifungal susceptibility testing, if necessary. CSF specimens submitted to monitor antigen levels during treatment do not need to be cultured.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Patients having trichosporonosis may yield false-positive results.

 

Rheumatoid factor may produce false-positive results.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

If positive, results are titered.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Warren NG, Hazen KC: Candida, Cryptococcus, and other yeasts of medical importance. In Manual of Clinical Microbiology. Seventh edition. Edited by PR Murray. Washington, DC, ASM Press, 1999, pp 1184-1199

2. Lu H, Zhou Y, Yin Y, et al: Cryptococcal antigen test revisited: significance for cryptococcal meningitis therapy monitoring in a tertiary Chinese hospital. J Clin Microbiol 2005 June;43(6):2989-2990


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