Array Comparative Genomic Hybridization (aCGH)
Array Comparative Genomic Hybridization (aCGH) is an advanced technique used to analyze DNA and detect genetic imbalances, such as duplications (gains) or deletions (losses) of genetic material across the genome. This test is a powerful tool for diagnosing genetic disorders, particularly in cases involving congenital abnormalities, intellectual disabilities, developmental disorders, and infertility.
How Does aCGH Work?
aCGH works by comparing a patient’s DNA with a reference sample using a microarray containing hundreds of thousands of genetic probes, allowing for highly accurate detection of genetic variations.
- DNA Sample Collection: DNA can be extracted from blood, amniotic fluid (during pregnancy), or tissues from the placenta or fetus.
- Sample Preparation and Analysis: The extracted DNA is labeled with a fluorescent dye and compared to a normal reference sample.
- Genetic Hybridization: The two DNA samples are combined on a microarray chip containing precise genetic probes that interact with the DNA, revealing any genetic gains or losses.
- Result Analysis: A laser scanner examines the chip, and differences in fluorescence intensity indicate the presence of a mutation or chromosomal abnormality.
Why is aCGH Performed?
During Pregnancy and Prenatal Diagnosis
- Detecting genetic disorders in embryos when abnormal ultrasound (sonogram) findings are present.
- Screening amniotic fluid or chorionic villi for Down syndrome and other chromosomal syndromes.
- Diagnosing cases of recurrent pregnancy loss and unexplained miscarriages.
In Infants and Newborns
- Evaluating unexplained developmental and cognitive delays.
- Diagnosing genetic neurological disorders such as autism, speech delays, and learning difficulties.
- Identifying unknown congenital defects, including heart or skeletal abnormalities.
In Infertility and IVF Failure Cases
- Assessing couples experiencing repeated pregnancy failure or abnormalities in sperm or eggs.
- Identifying genetic imbalances that may affect embryo health before implantation.
Advantages of aCGH
- High Accuracy: Detects minute genetic changes that traditional tests cannot identify.
- Comprehensive Genome Coverage: Analyzes all chromosomes at once rather than focusing on specific regions.
- Faster Results: The analysis takes less time compared to conventional chromosomal testing.
- No Need for Cell Culturing: Reducing the risk of test failure compared to traditional karyotyping.
Understanding aCGH Results
- Normal Result: No abnormal genetic changes detected.
- Identified Genetic Disorder: Conditions such as DiGeorge syndrome (22q11.2 deletion) or Prader-Willi/Angelman syndrome (15q11-q13 deletion) may be detected.
- Unknown Genetic Variation: In some cases, genetic counseling may be required to assess potential risks.
