What is the name of the blood test to detect folate (Folic acid) antibodies?

Blood Test for Folate Antibodies

The blood test for detecting folate antibodies is called the Folate Receptor Autoantibody Test, which measures both blocking and binding autoantibodies to folate receptor α (FRα) in serum. 1

Types of Folate Antibody Tests

The folate receptor autoantibody test can detect two distinct types of antibodies:

• Blocking antibodies - These interfere with folate transport by blocking the receptor
• Binding antibodies - These bind to the folate receptor and may cause inflammatory responses

Both IgG and IgM autoantibodies can be detected using these specialized assays 1. The predominant antibody isotypes vary by condition:

• In neural tube defect pregnancies: IgG1 and IgG2 isotypes
• In cerebral folate deficiency: IgG1 and IgG4 isotypes

Clinical Applications

This specialized test is particularly relevant in several clinical scenarios:

• Evaluation of pregnancy-related complications, especially neural tube defects
• Investigation of cerebral folate deficiency (CFD) syndrome in children
• Assessment of certain developmental disorders including autism spectrum disorders
• Cases where patients respond to folate therapy despite normal serum folate levels

Test Methodology

The folate receptor autoantibody test uses specific assays to measure the presence and concentration of these antibodies in serum. The test typically involves:

1. Isolation of patient serum
2. Detection of antibodies using specialized immunoassay techniques
3. Determination of antibody binding characteristics, affinity, and cross-reactivity

Distinguishing from Standard Folate Tests

It's important to note that this test differs from standard folate status assessment tests, which include:

• Serum folate (total B12/cobalamin) - Measures short-term folate status with standard cutoffs: <180 ng/L for confirmed deficiency 2
• Red blood cell folate - Assesses long-term folate status 2, 3
• Active B12 (holotranscobalamin) - More accurate than total B12 but still has limitations 2
• Methylmalonic acid (MMA) - Used as a confirmatory test in indeterminate cases 2

Clinical Significance

Detection of folate receptor autoantibodies is significant because:

• These antibodies can block folate transport even when serum folate levels appear normal
• Early detection and intervention could prevent or reverse consequences of exposure to these antibodies
• The presence of these antibodies may explain why some patients respond to folate therapy despite normal serum folate levels

Limitations and Considerations

• The folate receptor autoantibody test is not routinely available in all clinical laboratories
• Interpretation requires specialized knowledge of folate metabolism and transport
• Results should be considered alongside clinical presentation and other laboratory findings

Early detection of folate receptor autoantibodies is valuable as intervention with appropriate folate supplementation could potentially prevent or reverse the consequences of these antibodies on development and neurological function 1.