DiGeorge Syndrome by FISH Test
About DiGeorge Syndrome by FISH Test
| Field | Value |
|---|---|
| Also Known As | 22q11.2 Deletion FISH, DiGeorge/VCFS FISH, Velocardiofacial syndrome FISH, Shprintzen syndrome FISH, CATCH 22 FISH, 22q11.2 Microdeletion Test |
| Sample Type | Peripheral blood (sodium heparin tube); bone marrow; chorionic villus sampling (CVS); amniotic fluid; cord blood |
| Fasting Required | No |
| Report Time | 8 Days |
| Recommended For | All ages, including newborns, children, and adults with suspected 22q11.2 deletion; prenatal testing available |
| Price | Starting at ₹5,400 |
What is a DiGeorge Syndrome by FISH Test?
The DiGeorge Syndrome by FISH test is a specialised genetic test that checks for a tiny missing piece of chromosome 22, known as a 22q11.2 deletion. FISH stands for fluorescence in situ hybridisation, a laboratory technique that uses fluorescently labelled probes to identify whether a specific region of DNA is present or absent. Doctors order this test when a patient shows signs that may point to DiGeorge syndrome or a related condition. It is also known as the 22q11.2 microdeletion test, the Velocardiofacial syndrome FISH, or the CATCH 22 FISH test.
What Does a DiGeorge Syndrome by FISH Test Measure?
This test examines a specific region on chromosome 22 to determine whether genetic material is missing, present, or duplicated. The table below summarises what is assessed.
| What is Analysed | What it Tells Us |
|---|---|
| 22q11.2 chromosomal region | Whether the critical HIRA locus on the long arm of chromosome 22 is deleted, normal, or duplicated |
| Number of FISH signals per cell | Two signals are normal; one signal indicates a deletion; three signals indicate a duplication |
| Ten metaphase cells | Multiple cells are examined to confirm the finding and rule out technical errors |
The test detects deletions linked to DiGeorge syndrome and related conditions, as well as duplications linked to 22q11.2 duplication syndrome.
Why is a DiGeorge Syndrome by FISH Test Done?
A doctor may request the DiGeorge syndrome by FISH test when clinical features suggest a chromosomal deletion at 22q11.2, or when prenatal screening raises a concern. The sections below outline when this test is typically recommended.
Common Symptoms That May Require This Test
The following signs and symptoms are among the most common reasons a doctor may order this test:
- Congenital heart defects, particularly conotruncal malformations such as ventricular septal defect or tetralogy of Fallot
- Palate abnormalities, including cleft palate or velopharyngeal insufficiency
- Learning difficulties, developmental delay, or intellectual disability
- Recurrent infections or immune deficiency, including low T-cell counts
- Low blood calcium levels (hypocalcaemia), especially in newborns
- Gastrointestinal or kidney abnormalities detected at birth or on imaging
- Characteristic facial features noted by a clinician
Conditions This Test Can Help Detect
This test can help identify or confirm several related conditions. These include:
- DiGeorge syndrome (DGS)
- Velocardiofacial syndrome (VCFS), also called Shprintzen syndrome
- Conotruncal anomaly face syndrome
- 22q11.2 deletion syndrome (the umbrella term for all of the above)
- 22q11.2 duplication syndrome
- Psychiatric conditions and autoimmune disorders associated with 22q11.2 deletions
DiGeorge Syndrome by FISH Test During Pregnancy
Prenatal testing for DiGeorge syndrome is available and is performed using amniotic fluid or chorionic villus sampling (CVS). Common reasons for prenatal testing include a previous child with a confirmed 22q11.2 deletion, a parent known to carry the deletion, or an abnormal finding on foetal ultrasound such as a conotruncal heart defect. The DiGeorge Syndrome FISH test during pregnancy helps families and doctors prepare for appropriate care after birth.
How to Prepare and What to Expect
No special preparation is needed for the DiGeorge Syndrome by FISH test procedure. The sections below explain what to do before your appointment and what the collection process involves.
Do You Need to Fast?
No fasting is required for this test. You may eat and drink as normal before sample collection.
Practical Tips Before Your Test
Here are a few simple steps to ensure a smooth experience:
- Bring a detailed clinical history, including your symptoms, previous test results, and family history, as this is required for the test
- Inform the collection staff about any medications you are currently taking
- Wear a loose, short-sleeved top for easy access during blood collection
- If this is a prenatal test, follow any specific instructions provided by your obstetrician or genetic counsellor
Step-by-Step Procedure
The sample collection process varies depending on the type of sample being collected. Below are the procedures for each sample type.
Peripheral Blood (suitable for home collection)
- A trained phlebotomist cleans a vein in your arm and draws approximately 3 mL of blood into a sodium heparin (green-top) tube.
- The tube is gently inverted several times to mix the blood with the anticoagulant.
- The sample is stored at 2 to 8 degrees Celsius and dispatched to the laboratory promptly. It must not be frozen or centrifuged.
- At the laboratory, the blood cells are cultured for approximately 72 hours to produce enough cells for analysis.
- Fluorescently labelled probes are applied to the cells. A scientist examines ten metaphase cells under a microscope to count FISH signals.
- Results are prepared and delivered within 8 days.
Bone Marrow, Chorionic Villus Sampling (CVS), Amniotic Fluid, and Cord Blood (hospital collection only)
- These samples require collection by a trained medical professional in a hospital or clinical setting. Home collection is not available for these sample types.
- For CVS, a small sample of placental tissue is taken either through the abdomen or the cervix, usually between 10 and 13 weeks of pregnancy.
- For amniotic fluid, a fine needle is inserted into the womb under ultrasound guidance, usually between 15 and 20 weeks of pregnancy.
- Bone marrow and cord blood are collected by a specialist during a planned procedure.
- All samples are handled with care, labelled clearly, and transported to the laboratory at the required temperature without freezing.
- The laboratory processes the sample using the FISH method, and results are available within the stated turnaround time.
Factors That Can Affect Accuracy
Several factors can influence how reliable the test result is. These include:
- Sample freshness — delays in transport can reduce cell viability
- Use of the wrong anticoagulant tube (sodium heparin is required; EDTA is not acceptable)
- Freezing or centrifuging the sample before analysis
- Low-level mosaicism, where only some cells carry the deletion, which this test may not detect
- Very small deletions within the 22q11.2 region or distal deletions at chromosome 22q13.3, which may fall outside the probe's target area
Understanding Your DiGeorge Syndrome by FISH Test Results
Your results will show the number of FISH signals detected in the analysed cells. The table below provides a general guide to what each pattern means.
| FISH Signal Pattern | Interpretation |
|---|---|
| 2 signals (one on each chromosome 22) | Normal — no deletion or duplication detected |
| 1 signal | Deletion detected — consistent with 22q11.2 deletion syndrome (DiGeorge syndrome) |
| 3 signals | Duplication detected — consistent with 22q11.2 duplication syndrome |
These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain circumstances can affect how results should be read. Your doctor will consider these when reviewing your report.
Low-level mosaicism, where only a proportion of cells carry the deletion, may not be picked up by FISH. If clinical suspicion remains high after a normal result, chromosomal microarray may be recommended for a more detailed look. Additionally, approximately 10% of people who show features of DiGeorge syndrome do not have a 22q11.2 deletion. Their symptoms may be caused by mutations in other genes, maternal diabetes, foetal alcohol syndrome, or other factors, and these cannot be detected by this test.
How to Maintain Healthy Levels
Because this is a genetic test for a chromosomal condition, lifestyle changes cannot alter the result or prevent the condition. However, these general points are worth keeping in mind:
- If a deletion is confirmed, early involvement of a multidisciplinary team, including cardiologists, immunologists, and speech therapists, can help manage associated symptoms effectively
- Genetic counselling is recommended for individuals who receive a positive result, as well as for family members who may be at risk
- Staying informed and working closely with a specialist gives the best chance of timely and appropriate care
Lupin Diagnostics DiGeorge Syndrome by FISH Test Price and Home Collection
The DiGeorge syndrome by FISH test at Lupin Diagnostics costs ₹5,400. Home collection is available for peripheral blood samples. For all other sample types (bone marrow, CVS, amniotic fluid, and cord blood), the sample must be collected at a hospital or clinical centre.
| City | Approximate Price (₹) |
|---|---|
| BHOPAL | 5400 |
| CHENNAI | 5400 |
| HYDERABAD | 5400 |
| KOLKATA | 5400 |
| NAVI MUMBAI | 5400 |
| PUNE | 5400 |
Disclaimer: Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
Here is how to book your DiGeorge syndrome by FISH test online:
- Select the test on the Lupin Diagnostics website.
- Choose your city and preferred time slot.
- Opt for home sample collection by a certified phlebotomist (for peripheral blood), or visit your nearest Lupin Diagnostics centre or partner hospital for other sample types.
- Receive your report via email or WhatsApp within the stipulated turnaround time.
Home Collection
DiGeorge Syndrome by FISH test home collection is available for peripheral blood samples across cities where Lupin Diagnostics operates. All samples are processed in NABL-accredited laboratories by trained scientists. Your digital report is delivered directly to you via email or WhatsApp once it is ready.
Frequently Asked Questions
The DiGeorge Syndrome by FISH test detects a small deletion on chromosome 22, in the region known as 22q11.2. This deletion is linked to a group of conditions, including DiGeorge syndrome and velocardiofacial syndrome. It is ordered for newborns, children, or adults with clinical features that suggest these conditions, as well as for prenatal testing when a family history or abnormal scan raises concern.
No fasting is needed. You can eat and drink normally before your blood is collected. However, you should bring a detailed clinical history to your appointment, as this is required for the test.
The report is typically ready within 8 days. This turnaround accounts for the time needed to culture cells and complete the FISH analysis in the laboratory.
Yes. Prenatal testing is available using amniotic fluid or chorionic villus sampling (CVS). These procedures are carried out in a hospital by a qualified specialist. Indications include a family history of 22q11.2 deletion or an abnormal heart finding on the foetal scan.
FISH can identify the deletion in approximately 95% of affected individuals. However, very small deletions and low-level mosaicism may not be detected. If clinical signs are strong but the FISH result is normal, your doctor may suggest a chromosomal microarray for further investigation.
Yes. A person with a confirmed 22q11.2 deletion has a 50% chance of passing the deletion to each child. Genetic counselling is recommended for affected individuals and their partners when planning a family.
A positive result means a deletion or duplication of the 22q11.2 region was detected. Your doctor or a genetic counsellor will explain the implications and recommend the next steps. Management typically involves a team of specialists who address the heart, immune system, calcium levels, and developmental needs of the individual.
DiGeorge Syndrome by FISH Test
