Spino-Bulbar Muscular Atrophy Test
Short Name: SBMA Test
Also known as: Kennedy's disease, SBMA, Spinal and bulbar muscular atrophy
Spino-Bulbar Muscular Atrophy Test test available at DNA Labs India for ₹11,000. Uses PCR, Fragment Analysis on Whole Blood samples. Results in Samples received by Tuesday 11 AM are generally reported by Saturday. This may vary by location and laboratory workflow.. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr Pasupathy Arumugam
Consultant Pathologist · Reg: 21521
Last reviewed: September 7, 2026
Overview
The purpose of the SBMA test is to detect pathogenic CAG repeat expansion in the AR gene to confirm a clinical diagnosis of Kennedy's disease, distinguish it from other motor neuron disorders, identify at-risk carriers in the family, and inform genetic counselling and follow-up planning.
- Test Code
- 3661
- Price
- ₹11,000
- Sample Type
- Whole Blood
- Result Time
- Samples received by Tuesday 11 AM are generally reported by Saturday. This may vary by location and laboratory workflow.
- Fasting Required
- No
- Method
- PCR, Fragment Analysis
Sample Collection
No fasting is required. Complete the Genomics Clinical Information Requisition Form (Form 20) and ensure it is sent with the sample.
Method: Venipuncture
Laboratory Analysis
A trained phlebotomist will collect venous blood using a lavender-top EDTA tube.
Report Delivery
The sample should be refrigerated and transported to the laboratory. Do not freeze the sample.
Timeline: Samples received by Tuesday 11 AM are generally reported by Saturday. This may vary by location and laboratory workflow.
About This Test
Who Should Get This Test
The purpose of the SBMA test is to detect pathogenic CAG repeat expansion in the AR gene to confirm a clinical diagnosis of Kennedy's disease, distinguish it from other motor neuron disorders, identify at-risk carriers in the family, and inform genetic counselling and follow-up planning.
How to Prepare
- Duly filled Genomics Clinical Information Requisition Form (Form 20) is mandatory.
- Use a lavender-top EDTA tube.
- Minimum sample volume is 2 mL; 4 mL is preferred.
- Ship refrigerated; do not freeze.
- Transport within 6 hours at room temperature or within 1 week under refrigeration.
Doctor's Notes
Reviewed by Dr Pasupathy Arumugam — MBBS, MD (Pathology) · Reg. No. 21521
"A genetic test result should always be interpreted in the context of the clinical picture, family history, and electromyography findings. SBMA requires coordinated multidisciplinary care."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Missing or incomplete Form 20
- Frozen or thawed sample
- Clotted or haemolysed sample
- Insufficient sample volume
- Improperly labelled or expired tube
Understanding Your Results
Normal
AR allele contains 9-36 CAG repeats. No SBMA-associated expansion detected. Other neuromuscular causes should be considered if symptoms persist.
Expanded
AR allele contains >=38 CAG repeats. This is consistent with a diagnosis of SBMA in a male with compatible clinical features. Genetic counselling and family testing are recommended.
Uncertain/Borderline
Repeat size near the threshold should be interpreted with caution and may require testing of family members and specialist evaluation.
Consult a neurologist or clinical geneticist if you have progressive muscle weakness, swallowing or speech difficulty, muscle cramps, twitching, or a family history of SBMA. Do not use this test as a self-diagnostic tool.
Limitations
- ⚠This assay is designed to size the AR CAG repeat and does not analyse other genes.
- ⚠A normal result does not exclude all other motor neuron or neuromuscular disorders.
- ⚠The result must be correlated with clinical features, family history, and neuromuscular investigations.
Risks & Considerations
- ●Minimal discomfort during blood collection
- ●Rare bruising or haematoma at the venipuncture site
- ●Very low risk of infection
Interfering Factors
- ●Use of a non-EDTA tube or wrong anticoagulant
- ●Delay in sample transport beyond room-temperature stability
- ●Freezing of the whole blood sample
- ●Incomplete labelling or missing Form 20
Frequently Asked Questions
What is the Spino-Bulbar Muscular Atrophy (SBMA) test?
What is the cost of the SBMA test at DNA Labs India?
What sample is needed for the SBMA test?
Do I need to fast for the SBMA test?
Who should undergo the SBMA test?
What does an expanded AR CAG repeat result mean?
Can women be tested for SBMA?
How long does the report take?
Does the SBMA test distinguish SBMA from ALS?
Is the SBMA test covered by insurance?
Can I get home sample collection for this test?
Why is genetic counselling recommended with SBMA testing?
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