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HelpTest Code PLFA Cryptococcus Antigen Screen, Lateral Flow Assay, Pleural Fluid
Reporting Name
Cryptococcus Ag Screen, LFA, PFUseful For
Diagnosis of infection with Cryptococcus species
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| PLFAT | Cryptococcus Ag Titer, LFA, PF | No | No |
Testing Algorithm
If this screen is positive, the antigen titer will be performed at an additional charge.
Method Name
Lateral Flow Assay (LFA)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Pleural FluidAdditional Testing Requirements
Pleural fluid testing for cryptococcal antigen should also be submitted for routine fungal culture. Order FGEN / Fungal Culture, Routine.
Specimen Required
Container/Tube: Sterile vial
Specimen Volume: 0.5 mL
Specimen Minimum Volume
0.25
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Pleural Fluid | Refrigerated (preferred) | 21 days | |
| Frozen | 30 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Reference Values
Negative
Day(s) Performed
Monday through Sunday
CPT Code Information
87899-Cryptococcus Ag Screen, LFA, PF
87899-Cryptococcus Ag Titer, LFA, PF (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PLFA | Cryptococcus Ag Screen, LFA, PF | 29533-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 42396 | Cryptococcus Ag Screen, LFA, PF | 29533-7 |
Secondary ID
42396Highlights
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.
Disease States
- Cryptococcosis
Clinical Information
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 United States.
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.
Interpretation
The presence of cryptococcal antigen in pleural fluid is indicative of infection with Cryptococcus species.
Monitoring cryptococcal antigen levels as a means 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
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
1. Binnicker MJ, Jespersen DJ, Bestrom JE, Rollins LO: Comparison of four assays for the detection of cryptococcal antigen. Clin Vaccine Immunol. 2012 Dec;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
Method Description
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)
Report Available
Same day/1 to 2 daysSpecimen Retention Time
7 daysTest Classification
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.Forms
If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.