FISH - Microdeletion Detection for Williams Syndrome Test
Short Name: Williams Syndrome FISH Test
Also known as: Williams Syndrome FISH Test, ELN Gene Deletion Test, Chromosome 7q11.23 Microdeletion FISH, Williams-Beuren Syndrome FISH Detection, WS Microdeletion Detection by FISH
FISH - Microdeletion Detection for Williams Syndrome Test test available at DNA Labs India for ₹8,500. Uses FISH (Fluorescence In Situ Hybridization) on Whole Blood samples. Results in Sample acceptance is daily by 4:00 PM. Reports are available within 4 working days from the date of sample receipt at the laboratory.. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr SULOCHANA HEMCHANDRA HOLLA
Consultant Medical Geneticist · Reg: 8532
Last reviewed: September 7, 2026
Overview
The primary purpose of the FISH - Microdeletion Detection for Williams Syndrome Test is to confirm or rule out the diagnosis of Williams Syndrome by detecting the deletion of the ELN gene and surrounding genes at chromosome 7q11.23. This test is essential for establishing a definitive molecular diagnosis when clinical features suggest Williams Syndrome. It helps differentiate Williams Syndrome from other genetic conditions with overlapping features, guides clinical management by identifying cardiac and developmental risks, and supports informed genetic counseling for affected families regarding recurrence risk and family planning.
- Test Code
- 594
- CPT Code
- 88271
- ICD Code
- Q87.89
- Price
- ₹8,500
- Sample Type
- Whole Blood
- Result Time
- Sample acceptance is daily by 4:00 PM. Reports are available within 4 working days from the date of sample receipt at the laboratory.
- Fasting Required
- No
- Method
- FISH (Fluorescence In Situ Hybridization)
Sample Collection
No special preparation such as fasting is required. Ensure that the Chromosome and FISH Analysis Requisition Form (Form 17) is duly filled and accompanies the sample. Inform the collection center of any ongoing medications or recent blood transfusions.
Method: Venipuncture
Laboratory Analysis
A venipuncture will be performed to collect 5 mL of whole blood into a Sodium Heparin (Green Top) tube. The collection is a routine blood draw and typically takes less than 5 minutes.
Report Delivery
Apply pressure to the puncture site with a cotton ball or gauze for 3 to 5 minutes to prevent bruising. The sample will be shipped at 18 to 22 degrees Celsius. Do not freeze the sample. Sample must reach the laboratory within 48 hours of collection for optimal results.
Timeline: Sample acceptance is daily by 4:00 PM. Reports are available within 4 working days from the date of sample receipt at the laboratory.
Patient Instructions
About This Test
Who Should Get This Test
The primary purpose of the FISH - Microdeletion Detection for Williams Syndrome Test is to confirm or rule out the diagnosis of Williams Syndrome by detecting the deletion of the ELN gene and surrounding genes at chromosome 7q11.23. This test is essential for establishing a definitive molecular diagnosis when clinical features suggest Williams Syndrome. It helps differentiate Williams Syndrome from other genetic conditions with overlapping features, guides clinical management by identifying cardiac and developmental risks, and supports informed genetic counseling for affected families regarding recurrence risk and family planning.
How to Prepare
- Collect 5 mL (minimum 3 mL) whole blood by venipuncture
- Use 1 Green Top (Sodium Heparin) tube only
- Ship the sample at 18 to 22 degrees Celsius room temperature
- DO NOT FREEZE the sample under any circumstances
- Duly filled Chromosome and FISH Analysis Requisition Form (Form 17) is mandatory with the sample
- Label the sample correctly with patient name, date of birth, and collection date
- Ensure the sample reaches the laboratory within 48 hours of collection
Doctor's Notes
Reviewed by Dr SULOCHANA HEMCHANDRA HOLLA — MBBS, MD (Medical Genetics) · Reg. No. 8532
"As an obstetrician and fetal medicine specialist, I frequently encounter prenatal and neonatal clinical features that warrant genetic evaluation for chromosomal microdeletion syndromes. The FISH test for Williams Syndrome is a critical diagnostic tool when a newborn or infant presents with supravalvular aortic stenosis, distinctive elfin-like facial features, feeding difficulties, or unexplained developmental delays. Because the deletion at 7q11.23 is too small for conventional karyotyping to detect, FISH remains the gold standard targeted test. Early confirmation of Williams Syndrome through this test enables timely cardiac surveillance, multidisciplinary developmental support, and informed genetic counseling for families planning future pregnancies. I strongly recommend this test for any infant or child where clinical suspicion exists."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Sample collected in EDTA (Purple Top) or any tube other than Sodium Heparin (Green Top)
- Frozen samples
- Hemolyzed or clotted blood samples
- Sample received after 48 hours of collection at room temperature
- Missing or incomplete Chromosome and FISH Analysis Requisition Form (Form 17)
- Sample volume less than 3 mL
Understanding Your Results
Two FISH signals detected (Normal / No Deletion)
The 7q11.23 region including the ELN gene is intact on both chromosomes. Williams Syndrome due to the classic 7q11.23 microdeletion is unlikely. If clinical suspicion remains high, further evaluation with chromosomal microarray or gene sequencing may be considered.
One FISH signal detected (Deletion / Positive for Williams Syndrome)
A hemizygous deletion at chromosome 7q11.23 is identified, consistent with a diagnosis of Williams Syndrome. Clinical correlation is recommended. Genetic counseling and further evaluation for associated cardiac, endocrine, and developmental features should be initiated.
Atypical or equivocal signal pattern
An unusual signal pattern may indicate a partial deletion, atypical rearrangement, or technical artifact. Repeat testing, additional FISH probes, or chromosomal microarray analysis is recommended for clarification.
Consult your doctor or a clinical geneticist if your child presents with distinctive facial features, unexplained developmental delays, heart murmurs or cardiac anomalies, feeding difficulties in infancy, hypersensitivity to sound, or if there is a family history of Williams Syndrome. Early consultation enables timely diagnosis, cardiac surveillance, and comprehensive developmental support.
Limitations
- ⚠This test specifically targets the 7q11.23 deletion and does not screen for other chromosomal abnormalities
- ⚠Rare cases of atypical or partial deletions in the Williams Syndrome critical region may not be detected
- ⚠Mosaicism may not be reliably identified if the deleted cell line is present at very low levels
- ⚠This test does not detect point mutations or other non-deletion variants in the ELN gene
- ⚠Results should be interpreted in conjunction with clinical findings and may require confirmatory testing such as chromosomal microarray analysis
Risks & Considerations
- ●Minor bruising or discomfort at the venipuncture site
- ●Rare risk of fainting during blood draw
- ●Very small risk of infection at the puncture site
Interfering Factors
- ●Sample collected in incorrect anticoagulant (must be Sodium Heparin, Green Top tube)
- ●Frozen or hemolyzed blood samples may yield unreliable results
- ●Failure to submit the duly filled Chromosome and FISH Analysis Requisition Form (Form 17) may delay processing
- ●Low cell viability due to delayed sample transport beyond 48 hours at room temperature
Compare With Similar Tests
| Test | FISH - Microdeletion Detection for Williams Syndrome Test | FISH for Williams Syndrome | Chromosomal Microarray (CMA) | Conventional Karyotyping | Whole Exome Sequencing (WES) |
|---|---|---|---|---|---|
| Comparison | FISH - Microdeletion Detection for Williams Syndrome Test |
Frequently Asked Questions
What is the FISH Microdeletion Detection for Williams Syndrome Test?
What is Williams Syndrome and what causes it?
Why is FISH used instead of a regular chromosome test for Williams Syndrome?
What sample is required for this test?
Is fasting required before this test?
How accurate is the FISH test for Williams Syndrome?
How long does it take to get the results?
What does a positive result mean?
What does a negative result mean?
Is this test available for prenatal diagnosis?
Does DNA Labs India offer home sample collection for this test?
What is the cost of the FISH Microdeletion Detection for Williams Syndrome Test?
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