Candida-Antibody Testing-Introduction, Principle, Purpose, Types of antibody tests, Limitation, and More

Introduction

Candida antibody testing measures immunoglobulins (IgG, IgA, and IgM) antibodies in the blood to help detect current or past Candida infections. These antibodies are produced in response to the presence of Candida in the body, assisting the immune system in fighting off the fungus.

Principle

• Immunoglobulin G (IgG): Indicates past or ongoing Candida infection. It generally appears about a week after exposure.
• Immunoglobulin A (IgA): Associated with mucosal membrane infections, such as in the gastrointestinal, respiratory, or genital tracts.
• Immunoglobulin M (IgM): Suggests a recent Candida infection. It is usually detectable in the bloodstream several days to a week after initial exposure. The elevated levels of IgM may indicate an acute response to Candida.

Purpose

• Diagnosis: Candida antibody testing can help diagnose invasive candidiasis, a serious fungal infection, especially in immunocompromised individuals.
• Monitoring: It can be applicable to monitor the effectiveness of antifungal treatment.

Key Points

Not a Definitive Diagnosis

A positive test doesn’t necessarily mean an active infection, as antibodies can persist after a past infection. 

Clinical Context

Test results should be interpreted in conjunction with a patient’s clinical presentation and other diagnostic findings. 

Limitations of the assay

Immunocompromised individuals may have reduced or variable antibody responses. 

Test Types:

Blood culture

A blood sample is sent to a clinical laboratory to see if Candida grows.

Mannan antigen and anti-mannan antibody

Mannan, a carbohydrate in the Candida cell wall, is detectable in this test.

Candida albicans germ tube antibody (CAGTA)

This assay detects antibodies against C. albicans, but may also detect other Candida species.

(1,3)-β-D-glucan (BDG)

Detects (1,3)-β-D-glucan, a carbohydrate found in the cell walls of many fungal species.

Polymerase Chain Reaction (PCR)

Some commercial Polymerase Chain Reaction (PCR) tests are available for detecting Candida, but there’s no FDA-approved test. 

Further Readings

1. https://www.webmd.com/skin-problems-and-treatments/what-to-know-candidiasis-tests#:~:text=Blood%20culture%20test.,krusei.
2. https://nutripath.com.au/product/candida-antibodies-antigen-test-code-3001-or-3002/
3. https://www.medichecks.com/products/candida-antibodies-blood-test
4. https://www.dynacare.ca/SpecialPages/SecondaryNav/Find-a-Test/NAT/CANDIDA%C2%A0ANTIBODIES%C2%A0IgA,IgG,IgM-(1)?sr=NAT&sa=C#:~:text=CANDIDA%20ANTIBODIES%20IgA%2CIgG%2CIgM%20(National),NEGATIVE
5. https://www.labcorp.com/tests/163135/candida-antibodies-iga-igg-igm-elisa#:~:text=A%20positive%20test%20does%20not%20necessarily%20indicate,patients%20who%20have%20no%20obvious%20Candida%20infection.