Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test
About Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test
| Field | Value |
|---|---|
| Also Known As | PWS/AS FISH Test, Chromosome 15q11.2-q13 Deletion Test, 15q11-q13 Microdeletion Analysis Test, PWS-AS Karyotype and FISH Test |
| Sample Type | Peripheral blood (sodium heparin tube) |
| Fasting Required | No fasting required |
| Report Time | 12 days |
| Recommended For | Infants, children, and adults of any gender with suspected PWS or AS symptoms |
| Price | Starting at ₹7,800 |
What Is a Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test?
The Prader-Willi/Angelman Syndrome (Karyotyping + FISH) test analyses chromosomes in a peripheral blood sample to detect genetic changes linked to two rare conditions: Prader-Willi syndrome (PWS) and Angelman syndrome (AS).
It combines karyotyping, which examines all chromosomes for structural problems, with FISH (Fluorescence In Situ Hybridisation), which targets a specific region on chromosome 15. Doctors order this test when a child or adult shows symptoms that suggest either of these genetic conditions. It is also known as the PWS/AS FISH test and the 15q11-q13 Microdeletion Analysis test.
What Does a Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test Measure?
This test examines chromosomes at two levels. The table below explains what each component looks for.
| Component | What It Examines |
|---|---|
| Karyotyping | The total number and structure of all 46 chromosomes; detects large deletions, rearrangements, or translocations |
| FISH for SNRPN locus (15q11.2) | Uses fluorescent probes to check for a missing segment on chromosome 15; two signals are expected, one on each copy of chromosome 15 |
| Chromosome 15 structure | Checks for deletions, translocations, or rearrangements in the 15q11-q13 region specifically |
The 15q11-q13 region on chromosome 15 contains imprinted genes. When expression from this region is lost, it leads to either PWS or AS depending on which parent's chromosome is affected.
Why Is a Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test Done?
This Karyotyping + FISH test is used when a doctor suspects a chromosomal cause behind specific developmental or physical symptoms.
Common Symptoms That May Require This Test
The following signs are common reasons a doctor may recommend this test:
- Very weak muscle tone (hypotonia) and poor feeding in newborns or infants
- Delayed developmental milestones such as inability to sit unsupported or make babbling sounds by 6 to 12 months of age
- Excessive hunger and early-onset obesity in young children
- Severe speech delay or near-absent spoken language
- Frequent seizures combined with balance and walking difficulties
- Frequent smiling, laughter, or unusually happy behaviour not matching the setting (a characteristic feature of Angelman syndrome)
- Short stature, small hands and feet, and mild intellectual disability
Conditions This Test Can Help Detect
This Prader-Willi/Angelman Syndrome (Karyotyping + FISH) test can help identify the following conditions:
- Prader-Willi syndrome, caused in approximately 70% of cases by a deletion on the paternal copy of chromosome 15
- Angelman syndrome, caused in approximately 70% of cases by a deletion on the maternal copy of chromosome 15
- Chromosomal translocations or structural rearrangements involving chromosome 15
How to Prepare and What to Expect
The Prader-Willi/Angelman Syndrome (Karyotyping + FISH) test procedure is straightforward and does not require any special preparation beyond what is noted below:
Do You Need to Fast?
No fasting is required before this test. You or your child can eat and drink normally before the appointment.
Practical Tips Before Your Test
Here are a few simple steps to ensure a smooth collection:
- Bring a detailed clinical history, including symptoms, previous test results, and family history
- If the patient has recently had a whole blood transfusion, inform the doctor; sample collection should be delayed by at least 10 days after transfusion
- Wear clothing with sleeves that can be rolled up easily to allow access to the arm vein
- Keep the patient well hydrated, as this makes blood collection easier
- Carry any previous genetic test reports or referral letters to your appointment
Step-by-Step Procedure
The blood sample is collected from a vein using a standard process:
- A trained phlebotomist cleans the skin over a vein, usually inside the elbow or forearm
- A small needle is inserted, and approximately 3 ml of blood is drawn into a sodium heparin (green-top) tube
- The tube is gently mixed and labelled with the patient's name and date of birth
- The sample is kept at the correct storage temperature and transported to the laboratory without freezing or centrifuging
- In the laboratory, cells are cultured and stained for karyotyping; a microscopist then examines the chromosomes under a microscope
- For the FISH portion, fluorescent probes are applied to the chromosome 15 region and examined to detect the presence or absence of the target genetic segment
Factors That Can Affect Accuracy
The following factors may influence how reliable the results are:
- Poor sample quality or low cell viability at the time of collection
- Incorrect storage or transport conditions, particularly if the sample is accidentally frozen
- Recent blood transfusion (which can introduce donor DNA into the sample)
- The test does not detect all causes of PWS or AS; uniparental disomy (where both copies of chromosome 15 come from the same parent) and imprinting defects require separate testing
Understanding Your Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test Results
Results should always be reviewed with a qualified geneticist or doctor who can interpret findings in the context of the patient's symptoms and family history.
| Parameter | Normal Finding | Abnormal Finding |
|---|---|---|
| Karyotype | 46,XX (female) or 46,XY (male); no structural changes | Deletion, translocation, or rearrangement on chromosome 15 |
| FISH for SNRPN locus (15q11.2) | Two signals present, one on each chromosome 15 | One signal absent, indicating a deletion in the 15q11-q13 region |
| Chromosome 15 structure | No deletions or rearrangements in the 15q11-q13 region | Structural abnormality detected |
Disclaimer: This information serves as a general guide. Your doctor will evaluate your cytogenetic results alongside your clinical background, symptoms, and other diagnostic findings. Always consult a qualified healthcare professional for personalised medical advice.
Understanding Risk and Next Steps
As this is a genetic test, the conditions it detects are not caused by lifestyle choices and cannot be prevented through diet or exercise. The following points may be helpful to families:
- Genetic counselling is strongly recommended for families with a history of PWS or AS to understand the implications of a positive result and to support informed family planning decisions
- A normal result does not completely rule out PWS or AS; some cases are caused by mechanisms that this test cannot detect, and further testing may be advised by your doctor
- Early identification of either syndrome allows families and healthcare teams to plan appropriate supportive care and developmental intervention
Lupin Diagnostics Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test Price and Home Collection
The Prader-Willi/Angelman Syndrome (Karyotyping + FISH) test cost at Lupin Diagnostics starts at ₹7,800, and home sample collection is available in select cities.
| City | Approximate Price (₹) |
|---|---|
| Mumbai | 7800 |
| Pune | 7800 |
| Bangalore | 7800 |
| Chennai | 7800 |
Disclaimer: Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
Follow these steps to book your Prader-Willi/Angelman Syndrome (Karyotyping + 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, or visit your nearest Lupin Diagnostics centre
- Receive your report via email or WhatsApp within the stipulated turnaround time
Home Collection
Lupin Diagnostics offers home collection for this test across multiple cities, allowing a trained phlebotomist to collect the peripheral blood sample at a time that suits you. All samples are processed in NABL-accredited laboratories by experienced staff. Digital reports are shared via email or WhatsApp once the results are ready.
Frequently Asked Questions
Karyotyping examines all 46 chromosomes under a microscope to detect large-scale structural changes. FISH uses fluorescent probes to zoom in on the specific 15q11-q13 region and detect smaller deletions that karyotyping might miss. Performing both together gives a more complete picture for diagnosing PWS or AS.
Testing can be done at any age, including in newborns. For PWS, testing is often prompted by severe hypotonia and feeding problems in newborns. For AS, symptoms such as developmental delay and seizures usually become noticeable between 6 months and 6 years of age.
The report is typically available within 12 days. Karyotyping requires cells to be cultured in the laboratory first, which takes time. The FISH component is usually faster, but both are processed together before the final report is released.
No. The test detects chromosomal deletions in the 15q11-q13 region, which account for approximately 70% of cases of both syndromes. Cases caused by uniparental disomy (where both chromosome 15 copies come from one parent) or imprinting defects require additional, separate testing. Your doctor will advise on next steps if the result is normal but symptoms remain.
Yes. The laboratory requires a detailed clinical history to process and interpret results accurately. Please bring a written summary of the patient's symptoms, developmental milestones, previous test reports, and any relevant family history to your appointment or home collection visit.
Prenatal testing through amniocentesis or chorionic villus sampling is an option for at-risk pregnancies where there is a confirmed family history. This is a separate procedure from the Karyotyping + FISH test done on an infant or child and should be discussed with a geneticist or specialist.
Yes. Genetic counselling is strongly advised both before and after this test. A genetic counsellor can help families understand what a positive or inconclusive result means, explain the likelihood of recurrence in future pregnancies, and guide families on appropriate next steps.
Prader-Willi/Angelman Syndrome (Karyotyping + FISH) Test
