FISH - Neonatal Screen (5 Probes for Trisomy 13, 18, 21, X, Y Test
FISH - Neonatal Screen (5 Probes for Trisomy 13, 18, 21, X, Y Test
The Fluorescence in Situ Hybridization (FISH) Neonatal Screen is a genetic test that uses fluorescent probes to detect chromosomal abnormalities in newborns. This test screens for common aneuploidies, including trisomies 13, 18, and 21, and abnormalities in the sex chromosomes (X and Y). FISH is a rapid and reliable diagnostic tool, often used in critical neonatal settings where early detection of chromosomal disorders is crucial.
What is the FISH - Neonatal Screen Used For?
This test is primarily used to:
- Detect Chromosomal Aneuploidies: Identify extra or missing chromosomes linked to specific genetic disorders.
- Diagnose Congenital Conditions: Confirm conditions like Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), or Patau syndrome (Trisomy 13).
- Identify Sex Chromosome Abnormalities: Detect conditions like Turner syndrome (monosomy X), Klinefelter syndrome (XXY), or other sex chromosome aneuploidies.
- Guide Early Intervention: Facilitate timely medical care and genetic counseling for affected newborns.
Conditions Screened by the FISH Neonatal Screen
Trisomy 13 (Patau Syndrome)
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- Associated with severe intellectual disability, heart defects, cleft lip/palate, and polydactyly (extra fingers or toes).
Trisomy 18 (Edwards Syndrome)
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- Causes growth retardation, heart abnormalities, and other life-limiting complications.
Trisomy 21 (Down Syndrome)
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- Characterized by developmental delays, intellectual disability, and distinct facial features.
Sex Chromosome Abnormalities (X and Y)
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- Conditions include:
- Turner Syndrome (Monosomy X): Short stature, infertility, and other physical features in females.
- Klinefelter Syndrome (XXY): Tall stature, reduced muscle mass, and infertility in males.
Symptoms Indicating the Need for the Test
The FISH Neonatal Screen is recommended if the newborn shows
Physical features suggestive of chromosomal abnormalities (e.g., distinct facial features, congenital malformations)
Low birth weight or failure to thrive
Developmental delays or hypotonia (low muscle tone)
Ambiguous genitalia or other signs of sex chromosome anomalies
A family history of chromosomal disorders
Preparation for the Test
No special preparation is needed for the FISH Neonatal Screen. Key considerations include:
- Sample Collection: The test typically uses a blood sample from the newborn. In some cases, tissue samples may also be used.
- Timing: The test is often ordered within the first few days of life when abnormalities are suspected.
- Parental Consent: Ensure informed consent is obtained before performing genetic testing.
Interpretation of Results
The FISH test provides rapid results, often within 24–48 hours, and identifies chromosomal abnormalities as follows:
- Normal Result:
- Indicates no detected abnormalities in chromosomes 13, 18, 21, X, or Y.
- Abnormal Result:
- Trisomy Detected: Confirms extra copies of chromosomes 13, 18, or 21.
- Sex Chromosome Aneuploidy Detected: Identifies conditions like Turner or Klinefelter syndrome.
Abnormal results typically require confirmation with a karyotype analysis or additional genetic testing.
FAQs
What is FISH, and how does it work?
FISH uses fluorescent probes that bind to specific DNA sequences on chromosomes, allowing visualization of chromosomal abnormalities under a fluorescence microscope.
Can this test diagnose all genetic conditions?
No, the FISH Neonatal Screen focuses on detecting specific aneuploidies for chromosomes 13, 18, 21, X, and Y. Other genetic tests may be required for a comprehensive evaluation.
Is FISH a confirmatory test?
While FISH is highly accurate and rapid, confirmatory tests like a full karyotype or chromosomal microarray analysis are often performed for definitive diagnosis.
Does a normal result rule out genetic disorders?
No, a normal FISH result excludes the specific aneuploidies tested but does not rule out other genetic or metabolic disorders.
Can this test be performed prenatally?
Yes, FISH can also be performed on amniotic fluid or chorionic villus samples during pregnancy to detect chromosomal abnormalities.
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