What is FRAT®?

What is FRAT®?

FRAT® is an acronym for Folate Receptor Autoantibody Test. Indeed, a clever name for a clever and vital test!

The folate receptor autoantibody test (FRAT®) is a diagnostic tool used to detect the presence of autoantibodies against folate receptors in the body. These autoantibodies can interfere with the normal binding and transport of folate (vitamin B9) into cells, potentially leading to various health issues, particularly in the brain, nervous system and during pregnancy.

It is important to know if these autoantibodies exist. Their presence will signal an indication that there may be a problem with the transport of folate (vitamin B9). In other words, folate may not be getting into vital tissues and organs, specifically the brain and central nervous system (CNS).

Where is FRAT® performed?

FRAT® is performed in a CLIA certified laboratory. CLIA stands for the Clinical Laboratory Improvement Amendments. It is a set of United States federal regulatory standards that apply to all clinical laboratory testing performed on humans. The CLIA program is administered by the Centers for Medicare & Medicaid Services (CMS) and aims to ensure quality laboratory testing, with accurate testing and timely results.

Known as a Lab Developed Test (LDT), FRAT® requires the prescription of a medical professional. This is to ensure proper interpretation of results and proper follow-up and guidance with any potential treatments or therapies.

How the Test Works:

  1. Sample Collection: A blood sample is collected from the patient. FRAT® generally requires 1 to 2 ml of blood. The sample is then processed to obtain serum which contains the antibodies.
  2. Detection Method: The test typically employs an immunoassay technique, such as enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA). These methods can accurately detect and measure the concentration of autoantibodies in the blood. The intensity of the signal is proportional to the amount of folate receptor autoantibodies in the patient’s serum.

FRAT® Detection of Two Types of Autoantibodies:

FRAT® screens for two distinct autoantibodies to the folate receptor. These are blocking autoantibodies and binding autoantibodies.

Folate receptor blocking autoantibodies prevent folate from binding to its receptor. These autoantibodies specifically interfere with the binding site of the folate receptor, directly blocking folate from attaching to its receptor. This blockage prevents folate from being transported into cells, leading to a reduction in intracellular folate levels.

Folate receptor binding autoantibodies attach to the folate receptors without necessarily interfering with the binding of folate itself. These autoantibodies bind to the folate receptors, potentially altering their function or the cell’s ability to transport folate. The binding can cause an immune response or influence receptor function, but folate can still bind to its receptor. The presence of these autoantibodies can lead to altered receptor function and may contribute to conditions associated with folate deficiency.

Patients may have either blocking or binding autoantibodies and, in some cases, they may have both. Regardless of the type of autoantibody, the effects are somewhat similar as there is an impediment in folate transport.


  • The inhibition of folate binding and transport can lead to a functional folate deficiency, even if folate levels in the blood are normal.
  • Conditions associated with these autoantibodies include neurological disorders, developmental delays, and possibly other systemic effects due to impaired folate uptake.

Interpretation of Results

  • Positive Result: Indicates the presence of folate receptor autoantibodies. This may suggest an autoimmune response affecting folate transport. It can be associated with conditions such as cerebral folate deficiency, neural tube defects, or certain neurological disorders.
  • Negative Result: Indicates the absence of folate receptor autoantibodies, suggesting normal folate transport and no autoimmune interference.

Clinical Significance

Detecting folate receptor autoantibodies is important in diagnosing and managing conditions related to folate deficiency or impaired folate transport, including:

  • Neurological Disorders: Such as autism spectrum disorders and neurodevelopmental delays, where folate metabolism is crucial.
  • Pregnancy Complications: Folate is vital for fetal development, and its deficiency or impaired transport can lead to neural tube defects and other developmental issues.
  • Cerebral Folate Deficiency: A condition characterized by low levels of folate in the cerebrospinal fluid despite normal blood levels, often associated with neurological symptoms.

Overall, FRAT® (folate receptor autoantibody test) is a valuable diagnostic tool that helps identify autoimmune interference with folate metabolism, enabling appropriate interventions to ensure adequate folate availability and prevent related health issues.

As with any medical condition or medical diagnostic please consult your physician.

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