Test Id : PLFA
Cryptococcus Antigen Screen, Lateral Flow Assay, Pleural Fluid
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosis of infection with Cryptococcus species
Highlights
This test can be used as an adjunct for diagnosis of pulmonary infection with Cryptococcus species. Positive results are indicative of infection; however, cryptococcal antigen may remain detectable for prolonged periods of time following disease resolution.
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 |
|---|---|---|---|
| PLFAT | Cryptococcus Ag Titer, LFA, PF | No | No |
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If this screen is positive, the antigen 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
Aliases
Lists additional common names for a test, as an aid in searching
Crypto
Thoracentesis Fluid
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If this screen is positive, the antigen titer will be performed at an additional charge.
Specimen Type
Describes the specimen type validated for testing
Pleural Fluid
Additional Testing Requirements
Pleural fluid testing for cryptococcal antigen should also be submitted for routine fungal culture. Order FGEN / Fungal Culture, Routine.
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Container/Tube: Sterile vial
Specimen Volume: 0.5 mL
Forms
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. The minimum volume is sufficient for one attempt at testing.
0.25
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
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 |
|---|---|---|---|
| Pleural Fluid | Refrigerated (preferred) | 21 days | |
| Frozen | 30 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosis of infection with Cryptococcus species
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
If this screen is positive, the antigen 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 associated with tropical and subtropical regions only; however, more recently this organism has also been found to be endemic in British Columbia, along the Pacific Northwest, and in the Southeastern US.
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.
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.
Negative
Interpretation
Provides information to assist in interpretation of the test results
The presence of cryptococcal antigen in pleural fluid is indicative of infection with Cryptococcus species.
Monitoring cryptococcal antigen levels to determine response to therapy is discouraged, as antigen levels may persist despite adequate treatment and disease resolution.
A negative result indicates lack of infection; however, rare cases of false-negative results have been reported. Fungal culture should always be ordered alongside antigen testing.
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 diagnosis of cryptococcal infection, particularly if the patient is at risk for cryptococcosis and shows symptoms consistent with this disease.
False-positive results may occur in patients with trichosporonosis or infection with Capnocytophaga species.
Supportive Data
Sixty pleural fluid samples, including 30 specimens collected from patients without microbiologic testing ordered and 30 specimens spiked at various dilutions with Cryptococcus antigen (CrAg)-positive specimens, were evaluated by both the IMMY CrAg lateral flow assay (LFA) and the Meridian Cryptococcus antigen latex agglutination (CALAS) assays. The results are summarized in Table 1.
Table 1. Comparison of the IMMY CrAg LFA and the Meridian CALAS assays
| Meridian CALAS result | Positive agreement (95% CI) | Negative agreement (95% CI) | Overall agreement (95% CI) | |||
| Positive | Negative | 81% (65.4-90.8) | 100% (86.5-100) | 89.5% (79.6-95.1) | ||
| IMMY LFA result | Positive | 23 | 7(a) | |||
| Negative | 0 | 30 | ||||
(a)Details for these 7 discordant samples are provided in Table 2. All 7 specimens were pleural fluid spiked with CrAg-positive material and were expected to be positive by both assays.
Table 2. Comparison of discordant specimens between the IMMY CrAg LFA and Meridian CALAS Assays
| Sample | Meridian qualitative result | LFA qualitative result | LFA quantitative result |
| 1 | Negative | Positive | 1:10 |
| 2 | Negative | Positive | 1:2 |
| 3 | Negative | Positive | 1:10 |
| 4 | Negative | Positive | 1:2 |
| 5 | Negative | Positive | 1:5 |
| 6 | Negative | Positive | 1:160 |
| 7 | Negative | Positive | 1:80 |
The IMMY CrAg LFA has been shown to be significantly more sensitive in both serum and CSF specimens in prior studies.(1) Our findings in pleural fluid are consistent with these previous studies.
The reportable range for this assay is 1:2 to 1:2560 and the reference range is negative. Cross-reactivity was not observed with specimens positive for Histoplasma capsulatum or Aspergillus species antigens.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Binnicker MJ, Jespersen DJ, Bestrom JE, Rollins LO. Comparison of four assays for the detection of cryptococcal antigen. Clin Vaccine Immunol. 2012;19(12):1988-1990
2. Howell SA, Hazen KC, Brandt ME. Candida, cryptococcus, and other yeast of medical importance. In: Manual of Clinical Microbiology. 11th ed. ASM Press; 2015:1984-2014
3. Chang CC, Harrison TS, Bicanic TA, et al. Global guideline for the diagnosis and management of cryptococcosis: an initiative of the ECMM and ISHAM in cooperation with the ASM. [published correction appears in Lancet Infect Dis. 2024;24(8):e485. doi:10.1016/S1473-3099(24)00426-2]. Lancet Infect Dis. 2024;24(8):e495-e512. doi:10.1016/S1473-3099(23)00731-4
4. Perfect JR, Bicanic T. Cryptococcosis diagnosis and treatment: What do we know now. Fungal Genet Biol. 2015;78:49-54. doi:10.1016/j.fgb.2014.10.003
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-cryptococcal antigen monoclonal antibodies and gold-conjugated control antibodies deposited on the test membrane. If cryptococcal antigen is present in the specimen, it binds to the gold-conjugated anti-cryptococcal antigen antibodies. This complex wicks up the membrane and interacts with the test line, which has immobilized anti-cryptococcal 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.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
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 modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
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.
CPT codes are provided by the performing laboratory.
87899-Cryptococcus Ag Screen, LFA, PF
87899-Cryptococcus Ag Titer, LFA, PF (if appropriate)
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 |
|---|---|---|
| PLFA | Cryptococcus Ag Screen, LFA, PF | 29533-7 |
| 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.
|
|---|---|---|
| 42396 | Cryptococcus Ag Screen, LFA, PF | 29533-7 |