Explanation

Candida albicans IgA: what is measured?

Candida albicans is a yeast, a type of fungus, that lives on the skin and mucous membranes of many people without causing symptoms, for example in the mouth, the intestines and the vagina. IgA is the type of antibody that works mainly on mucous membranes. The test uses an ELISA (a laboratory antibody test) to measure IgA antibodies against Candida in the blood; for this, the laboratory sends the blood on to an external laboratory. The result shows that your immune system has had contact with the yeast, not whether there is an infection anywhere.

What can it detect?

Previous contact of the immune system with Candida, which occurs in many healthy people
In hospital, together with cultures and the Candida antigen: a possible clue to an invasive Candida infection (systemic candidiasis) in seriously ill patients or people with a weakened immune system

Result

What does the result mean?

Positive result

A positive result means that IgA antibodies against Candida were found. Because the yeast lives on the mucous membranes of the mouth, intestine or vagina in many people, this also occurs in healthy people. The result does not say where the yeast is or whether it is causing symptoms. It also cannot show 'Candida overgrowth' in the intestines: that is not a recognized diagnosis and the test has not been studied for it. With symptoms of the mouth, skin or vagina, looking at the spot itself and, if needed, a culture is more reliable than a blood test.

Negative result

A negative result means that no or few IgA antibodies against Candida were found. This does not rule out an infection, certainly not in people with a weakened immune system, who sometimes make few antibodies. For healthy people, a negative result has little meaning, because the test is not meant to explain symptoms.

After an abnormal result

A positive result in someone who is not seriously ill usually does not lead to treatment. With symptoms that look like a yeast infection of the mouth, skin or vagina, the GP assesses the spot itself and takes a culture if needed. A suspected invasive infection should be investigated in hospital.

Reliability

How reliable is the test?

Antibodies against Candida also occur in many healthy people. Even when an invasive Candida infection is suspected, their value is limited: according to the SWAB guideline on invasive fungal infections, the diagnosis rests on cultures. According to the laboratory, the test is meant for suspected systemic candidiasis and for unexplained fever in intensive care patients and people with a weakened immune system. In European research in such seriously ill patients, antibodies against part of the Candida cell wall (mannan) were positive in about 6 in 10 proven infections, but also in some patients without an infection; those figures come from a different test and do not automatically apply to this ELISA. Outside that situation, a positive result cannot be properly interpreted.

What can affect the result?

Many healthy people have antibodies due to normal contact with the yeast on skin and mucous membranes.
The result does not distinguish between carriage, a past infection and a current infection.
With IgA deficiency, which about 1 in 700 people have, the result can be wrongly negative.
Test methods and cut-off values differ between laboratories and are not standardized.

Who it is for

Who is the test useful for?

Useful for

The result is most meaningful in seriously ill people: the laboratory lists as indications suspected systemic candidiasis and unexplained fever in intensive care patients and people with a weakened immune system, and then as an addition to cultures in hospital. In people without symptoms, and with symptoms such as tiredness, a bloated feeling or bowel symptoms, the result says little, because antibodies also occur in many healthy people. A yeast infection of the mouth, skin or vagina can be recognized by the spot itself and, if needed, confirmed with a culture.

How common is it?

Candida lives on the skin and mucous membranes of many people without causing symptoms, for example in the mouth, intestines and vagina. Superficial infections such as thrush in babies and a vaginal yeast infection are common and can be recognized without a blood test. An invasive Candida infection, in which the yeast is in the blood or in organs, occurs almost only in seriously ill patients in hospital.

Thuisarts.nl and SWAB guideline on invasive fungal infections

Drawbacks and risks

A positive result is common in healthy people and can wrongly give the impression that vague symptoms are caused by Candida, leading to unnecessary diets or antifungal medicines.
As long as symptoms are attributed to Candida, another cause that can be treated may go unnoticed for longer.

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