What are other Names for this Test? (Equivalent Terms)

• Array CGH
• Array Comparative Genomic Hybridization
• Microarray-based CGH

What is Microarray-based Comparative Genomic Hybridization? (Background Information)

• Microarray-based Comparative Genomic Hybridization (Array CGH) is a specialized genetic testing technique that is used to detect chromosomal abnormalities that are too tiny to be detected using conventional microscopic studies
• Array CGH compares an individual’s DNA with a control DNA sample to identify differences between the two sets of DNAs. Microarrays work by exploiting the ability of a DNA molecule to hybridize to another DNA strand
  • A microarray is comprised of thousands of short sequences of DNA (or probes) arranged in a specific grid pattern on a glass side. After the individual’s DNA is chopped up or digested, the probes are labeled with fluorescent dye
  • The reference and patient samples are mixed together and applied to the chip. After hybridization takes place, the chip is scanned into a microarray machine. This machine measures the amount of fluorescence on each probe
  • A computer analytical software calculates the amount of fluorescence in each piece of DNA. If there is too much DNA, more red dye may be observed, indicating a duplication; and, if there is too little DNA, more green dye may be observed, indicating a deletion
• The DNA in the cells is double-stranded. Each strand contains a mixture of four bases, namely A, T, C, and G. The bases of each strand bind with each other to hold the DNA together. The DNA is only able to bind if the bases on the two strands are complementary to each other
• Microarray-based Comparative Genomic Hybridization allows for the detection of chromosome imbalances that are too small to be seen through microscopic analysis. Small submicroscopic alterations may still disrupt physical and mental health development in individuals, and the Array CGH is an important genetic test that can help diagnose many chromosomal disorders

Note: Molecular testing has limitations due to the molecular method and genetic mutational abnormalities being tested. This can affect the results on a case-by-case basis. Consultation with your healthcare provider will help in determining the right test and right molecular method, based on individual circumstances.

What are the Clinical Indications for performing the Microarray-based Comparative Genomic Hybridization?

Following are the clinical indicators for performing the Microarray-based Comparative Genomic Hybridization test: 

• To assist (and in some cases, confirm) the initial diagnosis
• If there is a family history of the medical disorder/condition
• To distinguish other conditions that have similar features (signs and symptoms)
• To help in determining treatment options

How is the Specimen Collected for the Microarray-based Comparative Genomic Hybridization?

Following specimens may be collected for Microarray-based Comparative Genomic Hybridization test:

• Blood
• Saliva

The specimen sample requirements may vary from lab to lab. Hence, it is important to contact the testing lab for exact specimen requirements, before initiating the testing process.

• Process of obtaining the sample: As outlined by the laboratory testing facility
• Preparation required: As outlined by the laboratory testing facility

Note:

• Depending on the location of testing, it may take up to 6-8 weeks turnaround time, to obtain the test results

Cost of Microarray-based Comparative Genomic Hybridization:

• The cost of the test procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities
• In many cases, an estimate may be provided before the test is conducted. The final amount may depend upon the findings during the test procedure and post-operative care that is necessary (if any)

What is the Significance of the Microarray-based Comparative Genomic Hybridization Result?

The results of the Microarray-based Comparative Genomic Hybridization (Array CGH) may indicate if any of the following chromosomal anomaly has taken place:

• Deletion/microdeletion
• Duplication/microduplication
• Number and types of genes involved (such as deleted/duplicated)

Advantages of Array CGH:

• Array CGH allows for the detection of duplications and deletions of all 46 chromosomes in a single test which is far more precise than typical chromosome analyses. It is for this reason that more children are diagnosed from an Array CGH than other specific genetic tests such as FISH
• Array CGH can identify what specific genes are included in a deletion or duplication. 

Limitations of Array CGH:

• Balanced chromosome rearrangements may not detected via this technique. This is because balanced chromosomal rearrangements do not result in duplications or deletions and are not capable of being detected through Array CGH
• Array CGH may also be unable to identify chromosomal changes that are unrelated to the individual’s medical health issue at the time of testing

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

Many laboratories may not have the capability to perform this test. Only highly-specialized labs with advanced facilities and testing procedures may perform this test.

Please visit our Laboratory Procedures Center for more physician-approved health information:

http://www.dovemed.com/common-procedures/procedures-laboratory/