Test Catalog

Test ID: SLFAT    
Cryptococcus Antigen Titer, Lateral Flow Assay, Serum

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

Monitoring Cryptococcus antigen titers in serum


Aiding in the diagnosis of cryptococcosis


This test should not be used as a test of cure or to guide treatment decisions.

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 Cryptococcus gattii. C neoformans has been isolated from several sites in nature, particularly weathered pigeon droppings. C gattii was previously associated with tropical and subtropical regions only, however, more recently this organism has also been found to be endemic in British Columbia and among the Pacific Northwest United States and is associated with several different trees species.


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 higher predilection for infection of healthy individuals.(1,2)


In addition to the lungs, cryptococcal infections frequently involve the central nervous system (CNS), particularly in patients infected with HIV. Mortality among patients with 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.

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.


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.    


Disseminated infection is usually accompanied by a positive serum test.


Declining titers may indicate regression of infection. However, monitoring titers to cryptococcal antigen should not be used as a test of cure or to guide treatment decisions. Low-level titers may persist for extended periods of time following appropriate therapy and resolution of infection.(3,4)

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

Cryptococcus antigen titers acquired by the lateral flow assay (LFA) may be higher than titers achieved by other Cryptococcus antigen assays. Titers acquired by different assay methods are not interchangeable.     


Cryptococcus antigen titers should be followed using the same assay.


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


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


Testing hemolyzed serum samples may lead to false-negative results due to the high background color on the lateral flow assay  strip.


Although rare, extremely high concentrations of cryptococcal antigen can result in weak test lines and in extreme instances, yield negative test results.


This assay has not been evaluated for cross reactivity in patients with trichosporonosis.

Supportive Data

End-point titers between the IMMY Cryptococcus antigen lateral flow assay (LFA) and the Meridian latex agglutination test were compared for 10 samples positive for Cryptococcus antigen. While the overall qualitative correlation was good, these data indicate that the end-point titer achieved by the IMMY LFA was at least 2-fold higher than that achieved by the Meridian latex agglutination assay in 8 of 10 (80%) serum samples. (Table 1).(5) Therefore, Cryptococcus antigen titers should be monitored by using the same method on serially collected samples; titers acquired by different methods are not interchangeable.


Reciprocal endpoint titer by:

Serum sample

Meridian latex agglutination
































* This sample showed 1+ reactivity by the Meridian latex agglutination assay upon screening but was interpreted as negative according to the package insert requirement for 2+ reactivity.

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

1. Speed B, Dunt D: Clinical and host differences between infections with the two varieties of Cryptococcus neoformans. Clin Infect Dis. 1995;21(1):28-34

2. Chen S, Sorrell T, Nimmo G, et al: Epidemiology and host- and variety-dependent characteristics of infection due to Cryptococcus neoformans in Australia and New Zealand. Australasian Cyrptococcoal Study Group. Clin Infect Dis. 2000;31(2):499-505

3. 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

4. Perfect JR, Dismukes WE, Dromer F, et al: Clinical practice guidelines for the management of cryptococcal disease: 2010 update by the Infectious Diseases Society of America. Clin Infect Dis. 2010;50:291-322

5. Binnicker MJ, Jespersen DJ, Bestrom JE, Rollins LO: A comparison of four assays for detection of cryptococcal antigen. Clin Vaccine Immunol. 2012 Dec;19(12):1988-1990

6. Warren NG, Hazen KC: Candida, Cryptococcus, and other yeasts of medical importance. In: Murray PR, ed. Manual of Clinical Microbiology. 7th ed. ASM Press; 1999: 1184-1199