Test Catalog

Test Id : SLFA

Cryptococcus Antigen Screen with Titer, Serum

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

Aiding in the diagnosis of cryptococcosis


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


This test should not be used as a screening procedure for the general populations.

Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.

Test Id Reporting Name Available Separately Always Performed
SLFAT Cryptococcus Ag Titer, LFA, S Yes No

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If result is positive, Cryptococcus titer will be performed at an additional charge.

Method Name
A short description of the method used to perform the test

Lateral Flow Assay (LFA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Cryptococcus Ag Screen w/Titer, S

Lists additional common names for a test, as an aid in searching

Cryptococcus Ag Screen, S

Cryptococcus gattii

Cryptococcus neoformans

Fungal Serology

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If result is positive, Cryptococcus titer will be performed at an additional charge.

Specimen Type
Describes the specimen type validated for testing


Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 14 days

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

Aiding in the diagnosis of cryptococcosis


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


This test should not be used as a screening procedure for the general populations.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If result is positive, Cryptococcus titer will be performed at an additional charge.

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 only associated with tropical and subtropical regions. More recently, however, this organism has been found to be endemic in British Columbia and the Pacific Northwestern United States and is associated with several different tree 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 is 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.


Provides information to assist in interpretation of the test results

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 to generate a titer value.


Disseminated infection is usually accompanied by a positive serum test.


Higher Cryptococcus antigen 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 or to guide treatment decisions. Low-level titers may persist for extended periods of time following appropriate therapy and the resolution of infection.(3)

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 diagnosis of cryptococcosis, particularly if only a single specimen has been tested and the patient shows symptoms consistent with cryptococcosis. 


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 specimens 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

There were 634 serum specimens (632 prospective and 2 archived) tested in a blinded fashion by the IMMY Cryptococcus antigen lateral flow assay (LFA), the Meridian latex agglutination (Meridian Bioscience Inc) assay, and the Meridian Cryptococcus antigen enzyme immunoassay (EIA) within a 24-hour period. Specimens with discordant results after initial testing were repeated by both assays during the same freeze/thaw cycle. The results are summarized in Table 1 and Table 2 below:


Table 1: Comparison of the IMMY LFA to the Meridian latex agglutination assay


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.

Sensitivity: 100% (9/9); 95% CI: 65.5%-100%

Specificity: 99.8% (624/625); 95% CI: 99.0%-99.9%

Overall Percent Agreement: 99.8% (633/634); 95% CI: 99.0%-99.9%


Table 2: Comparison of the IMMY LFA to the Meridian Cryptococcus antigen EIA

Meridian EIA


















*These 5 samples were positive by the Meridian latex agglutination assay

Sensitivity: 100% (5/5); CI: 51.7%-100%

Specificity: 99.2% (624/629); CI: 98.1%-99.7%

Overall Percent Agreement: 99.2% (629/634); CI: 98.1%-99.7%

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 Cryptococcal Study Group. Clin Infect Dis. 2000 Aug;31(2):499-505. doi: 10.1086/313992

3. 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 Feb 1;50(3):291-322

4. 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

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

6. Perfect JR: Cryptococcosis (Cryptococcus neoformans and Cryptococcus gattii). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:3146-3161

Method Description
Describes how the test is performed and provides a method-specific reference

The Cryptococcus antigen (CrAg) lateral flow assay is a sandwich immunochromatographic assay. Specimens and diluent are added to a test tube and the lateral flow device is added. The test uses specimen wicking to capture gold-conjugated, anti-Cryptococcus antigen monoclonal antibodies and gold-conjugated control antibodies deposited on the test membrane. If Cryptococcus antigen is present in the specimen, it binds to the gold-conjugated, anti-Cryptococcus antigen antibodies. This complex wicks up the membrane and interacts with the test line, which has immobilized anti-Cryptococcus antigen monoclonal antibodies. The antigen-antibody complex forms a sandwich at the test line causing a visible line to form. A valid test shows a visible line at the control line. Positive test results create 2 lines (control and specimen) while negative results form only the control line.(Package insert: CrAg Lateral Flow Assay. IMMY; Rev 06/27/2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 2 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
SLFA Cryptococcus Ag Screen w/Titer, S 29903-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
62075 Cryptococcus Ag Screen w/Titer, S 29903-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports