GAD 65 Antibody by IFA (for Paraneoplastic syndrome)
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It helps identify autoimmune neurologic disorders, type 1 diabetes, and certain paraneoplastic syndromes
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🧪 What is GAD65 Antibody by IFA?
GAD65 (Glutamic Acid Decarboxylase 65) is an autoantibody targeting the enzyme responsible for synthesizing GABA, the main inhibitory neurotransmitter in the CNS.
- The test detects GAD65 autoantibodies in blood or CSF using IFA (Indirect Immunofluorescence Assay).
- It helps identify autoimmune neurologic disorders, type 1 diabetes, and certain paraneoplastic syndromes.
❓ Why is the Test Done?
To detect GAD65 autoimmunity in:
- Neurological Autoimmune Disorders:
- Stiff-person syndrome (SPS)
- Autoimmune cerebellar ataxia
- Limbic encephalitis
- Epilepsy (autoimmune origin)
- Paraneoplastic neurologic syndromes
- Endocrine Autoimmunity:
- Type 1 Diabetes Mellitus (T1DM)
- Latent Autoimmune Diabetes in Adults (LADA)
- Paraneoplastic Syndromes:
- Rare neurological syndromes associated with cancer (often breast, lung, or thymoma)
🔬 Method: Indirect Immunofluorescence Assay (IFA)
- Patient serum is incubated on slides coated with tissue expressing GAD.
- Fluorescent antibodies are added to detect bound autoantibodies.
- Positive result shows fluorescence patterns indicating GAD65 autoantibodies.
📊 Normal Range
Test | Reference |
|---|---|
GAD65 Antibody (IFA) | Negative (no specific fluorescence detected) |
Some labs may report semi-quantitative values or titres (e.g., low, moderate, high positive).
📈 Interpretation of Results
Result | Possible Interpretation |
|---|---|
Negative | No GAD65 autoimmunity detected |
Low Positive | Early or mild autoimmune process (e.g., LADA, mild neurologic symptoms) |
High Positive | Strong association with autoimmune neurologic disorders or paraneoplastic syndromes |
🧠 Associated Organs and Conditions
System | Condition |
|---|---|
Nervous System | - Stiff-person syndrome (SPS) |
Pancreas (Islets of Langerhans) | Type 1 Diabetes, LADA |
Paraneoplastic Sites | Breast, lung (small cell), thymoma, other tumors with ectopic GAD expression |
🔄 Related / Follow-Up Tests
- Other Paraneoplastic Antibodies:
- Anti-Hu, Anti-Yo, Anti-Ri, Anti-Ma2, CRMP-5
- CSF Analysis: In neurologic disease
- MRI Brain: For limbic encephalitis or cerebellitis
- Electromyography (EMG): In stiff-person syndrome
- Cancer screening: Mammogram, CT thorax/abdomen, PET-CT
- C-peptide, HbA1c: In suspected LADA or diabetes
✅ Fasting Required?
Parameter | Fasting Required |
|---|---|
GAD65 Antibody (IFA) | ❌ No fasting required |
📝 Summary Table
Parameter | Details |
|---|---|
What | Detects autoantibodies against GAD65 enzyme using IFA |
Why | Diagnose autoimmune neurologic disorders, T1DM, paraneoplastic syndromes |
Normal Range | Negative (no autoantibodies) |
Positive Result | Indicates GAD65 autoimmunity (e.g., SPS, ataxia, limbic encephalitis, LADA) |
Associated Conditions | Stiff-person syndrome, paraneoplastic neurological syndromes, T1DM |
Follow-up Tests | Paraneoplastic panel, CSF, MRI, cancer screen |
Fasting Required | ❌ No |
How our test process works!
