Test Catalog

Test ID: ULFAT    
Cryptococcus Antigen Titer, Lateral Flow Assay, Urine

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

Aiding in the diagnosis of infection with Cryptococcus neoformans or C gattii

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 or C gattii. The organism has been isolated from several sites in nature, particularly weathered pigeon droppings.

 

Infection is usually acquired 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. While the majority of C neoformans infections occur in immunocompromised patient populations, C gattii has a predilection for infection of healthy hosts.

 

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

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.

Only orderable as a reflex. For more information see ULFA / Cryptococcus Antigen Screen, Lateral Flow Assay, Urine.

Interpretation Provides information to assist in interpretation of the test results

The presence of cryptococcal antigen (CrAg) in any body fluid is strongly suggestive of infection with Cryptococcus neoformans or C gattii.

 

Declining titers are suggestive of clinical response to therapy. However, monitoring CrAg titers should not be used as a test of cure, as low level titers may persist for extended periods of time following appropriate therapy and disease resolution.

 

In addition to testing for CrAg, patients with presumed disease due to C neoformans or C gattii should have appropriate clinical specimens (eg, blood, bronchoalveolar lavage fluid) submitted for routine smear and fungal culture.

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

A negative result does not preclude the diagnosis of cryptococcosis, particularly if only a single specimen has been tested and the patient shows symptoms consistent with cryptococcal infection.

 

A positive result is suggestive of cryptococcosis, however, all test results should be interpreted in light of other clinical findings.

 

Testing should not be performed as a screening procedure for the general population and should only be performed when clinical evidence suggests the cryptococcal disease.

 

Although rare, extremely high concentrations of cryptococcal antigen (CrAg) can result in weakly positive or falsely-negative results.

 

Patients with trichosporonosis or Capnocytophaga species infection may yield false-positive results.

 

If followed for clinical purposes, CrAg titers should be followed using the same assay.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Hazen KC, Howell SA: Candida, Cryptococcus, and other Yeasts of Medical Importance. In Manual of Clinical Microbiology. Ninth edition. Edited by PR Murray. Washington, DC, ASM Press, 2007, pp 1762-1788

2. Bruner KT, Franco-Paredes C, Henao-Martinez A, et al: Cryptococcus gattii Complex Infections in HIV-Infected Patients, Southeastern United States. EID 2018 Nov;24(11) doi.org/10.3201/eid2411.180787