Explanation

Candida albicans IgG: 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. The test uses an ELISA (a laboratory antibody test) to measure IgG antibodies that the immune system has made against this yeast; for this, the laboratory sends the blood on to an external laboratory. IgG antibodies develop after contact with the yeast and can then remain present for a long time. The result therefore shows that your immune system knows the yeast, not whether there is an infection anywhere now.

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 there are IgG antibodies against Candida in your blood. This is common in healthy people, because the yeast lives on the skin and mucous membranes of many people and because superficial infections such as thrush or a vaginal yeast infection are common. A positive result is therefore not proof of an infection. The result also does not show 'Candida overgrowth' in the intestines: that is not a recognized diagnosis and cannot be established with this test. Symptoms such as tiredness or a bloated feeling are not explained by it.

Negative result

A negative result means that no or few IgG antibodies against Candida were found. This does not rule out a Candida infection: people with a severely weakened immune system sometimes make few antibodies. In addition, a superficial infection of the mouth, skin or vagina is not diagnosed with a blood test, but recognized by the spot itself or confirmed with a culture. For healthy people, a negative result has little meaning.

After an abnormal result

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

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 blood culture is central to the diagnosis. 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, and also in some patients without an infection; those figures come from a different test and do not automatically apply to this ELISA. Because many healthy people have antibodies, a positive result outside that hospital situation 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 superficial infection and a current infection.
People with a severely weakened immune system sometimes make few antibodies, so the result can be negative even though there is an infection.
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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