What is the Folate Receptor Autoantibody Test (FRAT)?

The Folate Receptor Autoantibody Test (FRAT) is a specialised blood test that detects antibodies directed against the folate receptor alpha (FRα), a protein responsible for transporting folate into the brain and other tissues.

These autoantibodies can block or interfere with folate delivery across the blood–brain barrier, meaning the brain may not receive enough active folate despite normal blood levels.
Because folate is essential for neurological development, DNA synthesis, and neurotransmitter function, impaired transport can lead to a “functional” deficiency affecting cognitive and neurological health.

The test specifically measures blocking and binding autoantibodies, which either prevent folate from attaching to its receptor or disrupt its transport into cells.

Why do I need this test?

FRAT is used when there is suspicion that symptoms may be linked to disrupted folate metabolism at the neurological level rather than a simple dietary deficiency.

Autoantibodies to the folate receptor have been associated with conditions such as cerebral folate deficiency, neurodevelopmental disorders, and certain psychiatric or neurological presentations.
Research shows that these antibodies can interfere with the transport of 5-methyltetrahydrofolate (active folate) into the brain, contributing to cerebral folate deficiency syndromes.

They have also been reported in individuals with autism spectrum disorders and other neurodevelopmental conditions, highlighting the role of impaired folate transport rather than low intake alone.

This test may therefore be considered when investigating:

• Developmental or cognitive concerns

• Neurological or behavioural symptoms of unclear origin

• Suspected cerebral folate deficiency

• Cases where folate supplementation has not resolved symptoms

• Pregnancy or fertility contexts linked to folate transport issues

Benefits of the test

1. Identifies autoimmune interference with folate metabolism

2. Detects functional folate deficiency not visible on routine tests

3. Provides insight into neurological folate delivery

4. Helps guide targeted nutritional or medical strategies

5. Supports earlier investigation of complex neurodevelopmental cases

6. Uses a simple blood sample rather than invasive procedures

7. Differentiates between blocking and binding antibodies for deeper assessment

8. Enables earlier intervention where folate transport disruption is suspected

Step-by-step testing process

1. A standard blood sample is collected and sent to a specialist laboratory.

2. The sample is analysed using immunoassay methods to detect folate receptor autoantibodies.

3. Results identify whether blocking or binding antibodies are present and at what level.

4. Findings help clinicians evaluate whether impaired folate transport may be contributing to symptoms.

Your results explained

Negative result
No detectable autoantibodies; folate transport via FRα is unlikely to be impaired.

Positive result (binding antibodies)
Antibodies attach to the receptor and may trigger immune-mediated dysfunction or inflammation.

Positive result (blocking antibodies)
These prevent folate from entering the brain, potentially leading to cerebral folate deficiency despite adequate folate intake.

Importantly, FRAT does not diagnose a specific condition on its own; it indicates whether this autoimmune mechanism may be contributing to clinical symptoms and should be interpreted alongside clinical assessment.