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Test Code LFACX Cryptococcus Antigen with Reflex, Spinal Fluid

Useful For

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 performed as a screening procedure for the general population.

Disease States

  • Cryptococcosis

Profile Information

Test ID Reporting Name Available Separately Always Performed
CLFA Cryptococcus Ag Screen w/Titer, CSF Yes Yes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
CLFAT Cryptococcus Ag Titer, LFA, CSF Yes No
FGENC Fungal Culture, CSF Yes, (Order FGEN) No

Testing Algorithm

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

 

If Cryptococcus antigen titer is positive, then fungal culture will be performed at an additional charge.

Reporting Name

Cryptococcus Ag w/Reflex, LFA, CSF

Specimen Type

CSF


Specimen Required


Container/Tube: Sterile vial

Specimen Volume: 1 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis Reject

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 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 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

CRYPTOCOCCUS ANTIGEN SCREEN WITH TITER

Negative

Reference values apply to all ages.

 

CRYPTOCOCCUS ANTIGEN TITER, LFA

Negative

Reference values apply to all ages.

 

FUNGAL CULTURE

Negative

If positive, fungus will be identified.

Reference values apply to all ages.

Interpretation

The presence of cryptococcal antigen in any body fluid (serum or cerebrospinal fluid [CSF]) is indicative of cryptococcosis. Specimens that are positive by the lateral flow assay (LFA) screen are automatically repeated by the same method utilizing dilutions to generate a titer value. CSF specimens submitted for initial diagnosis that test positive by LFA should also be submitted for routine fungal culture. Culture can aid in differentiating between the 2 common Cryptococcus species causing disease (Cryptococcus neoformans and Cryptococcus gattii) and can be used for antifungal susceptibility testing, if necessary. CSF specimens submitted to monitor antigen levels during treatment do not need to be cultured.

 

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, as low-level titers may persist for extended periods of time following appropriate therapy and the resolution of infection.

Cautions

A traumatic lumbar puncture and contamination of the cerebrospinal fluid (CSF) specimen with plasma may lead to a positive Cryptococcus antigen result from CSF in patients without neuroinvasive cryptococcosis.

 

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.

 

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

 

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

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, anticryptococcal 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, anticryptococcal antigen antibodies. This complex wicks up the membrane and interacts with the test line, which has immobilized anticryptococcal 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)

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 to 35 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

87899-Cryptococcus Ag Screen w/Titer, CSF

87899-Cryptococcus Ag Titer, LFA, CSF (as appropriate)

87102-Fungal Culture, CSF (as appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LFACX Cryptococcus Ag w/Reflex, LFA, CSF 29896-8

 

Result ID Test Result Name Result LOINC Value
62074 Cryptococcus Ag Screen w/Titer, CSF 29896-8

Method Name

Lateral Flow Assay (LFA)

Test Classification

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.