What is a Chromosomal Microarray?
- Chromosomal Microarray (CMA) is a microchip-based testing platform that allows automated analysis of many pieces of DNA at once
- CMA analysis has the capacity to examine the whole human genome in a single chip with high resolution
- It provides unparalleled screening for deletions, duplications, loss of heterozygosity and aneuploidy detection for all chromosomes
- CMA chips use probes that hybridize with specific chromosomal regions to detect copy number variations (CNVs)
- CMA offers a combination of CNV and Single Nucleotide Polymorphisms (SNP)
When should you use a CMA?
CMA’s can be used for a wide variety of purposes, from Product of Conception (POC) analysis to the various neurological conditions.
- They are the first-tier test* for individuals with:
- Developmental disabilities
- Autism spectrum disorders
- Multiple congenital anomalies
- Mental retardation
- For individuals with seizures and other developmental problems for which a chromosomal basis is suspected
- Detection of CNV’s at a single exon-level ensuring the diagnosis of single-gene diseases too
The International Standard Cytogenetic Array (ISCA) Consortium has developed the following algorithm for the use of CMA**
** David T. Miller, Margaret P. Adam, Swaroop Aradhya, et al. “Consensus Statement: Chromosomal Microarray Is a First-Tier Clinical Diagnostic Test for Individuals with Developmental Disabilities or Congenital Anomalies” The American Journal of Human Genetics, Volume 86, Issue 5, Pages 749-764 (May 2010)
Disorders it detects
- Conditions characterized by intellectual disability such as
- Angelman syndrome
- Wolf-Hirschhorn syndrome
- Williams syndrome
- DiGeorge syndrome
- Prader-Willi syndrome
- Accurate identification of a number of chromosome disorders early in pregnancy, including all known microdeletion and microduplication syndromes
- Detection of a variety of gains or losses towards the ends (telomeres) of the chromosomes which are the important causes of many developmental disability syndromes
- Higher resolution
- Nearly double diagnostic yield
- Detection of maternal cell contamination
- Detection of uniparental disomy
What is the advantage that CMA brings to a clinical practice?
Compared to Karyotyping CMA offer the following advantages:
What are the different types of CMAs?
1. CytoScanTM Xon array
- Provides high-resolution DNA copy number analysis to detect gains and losses at the exon level.
- Detects loss of heterozygosity (LOH), regions identical by descent, and uniparental isodisomy (UPD) on a single array
- Extensive coverage for 4,53,076 exons is 17,974 genes with increased sensitivity and specificity in 7,000 clinically relevant genes
2. CytoScanTM 750K array
- Offers comprehensive gene-level coverage for known constitutional genes on a single array
- Ideas for investigation of neurological disorder
3. CytoScanTM Optima array
- Ideal for genetic analysis of POC
- Aneuploidy analysis
| Type | Number of CNV Probes used | Number of SNPs Covered | Recommended for |
|---|---|---|---|
| CytoScanTM Xon array | 6.55 million | 300,000 | Developmental Delay (DD), Mental Retardation (MR), Multiple Congenital Anomalies (MCA) and Autism Spectrum Disorders (ASD) |
| CytoScanTM 750K array | 750,436 | 200,436 | |
| CytoScanTM Optima array | 18,018 | 148,450 | POC Testing / Aneuploidy |
Why MedGenome for CMAs?
As the leader in genomic diagnostics in India, MedGenome offers cutting edge scientific offerings coupled with world-class result interpretation and genetic counselling for CMA testing. At MedGenome we have the following CMA offerings:
| Type | CytoScanTM Xon array | CytoScanTM 750K | CytoScanTM Optima |
|---|---|---|---|
| Number of CNV Probes used | 6.55 million | 750,436 | 18,018 |
| Number of SNPs Covered | 300,000 | 200,436 | 148,450 |
| Probe Density | > 500Kb | > 100Kb | > 200Kb |
| Deletion | > 25Kb | > 100kb | > 1 Mb |
| Duplication | > 200Kb | > 400kb | > 2 Mb |
| Loss of Heterozygosity | > 100Kb | > 5 Mb | > 5 Mb |
| Absence of Heterozygosity | > 3% of total autosomal (>3Mb LCSH) | > 3% of total autosomal (> 3Mb LCSH) | > Not Reported |
| Long Continuous Stretches of Heterozygosity | LCSH >8-15 Mb | LCSH >8-15 Mb | > Not Reported |
| Recommended | Prenatal Testing; including first-line screening for cases of Developmental Delay (DD), Mental Retardation (MR), Multiple Congenital Anomalies (MCA) and Autism Spectrum Disorders (ASD) | POC Testing | |
| TAT | 14 Working Days | 12 Working days | 12 Working days |
Test sample requirements
Blood (3-5ml in EDTA tubes)
Required forms
- Relevant clinical information including all the clinical presentations and symptoms
- Test request form
Turn around time (TAT)
- 12-14 working days
Extracted DNA samples (1µg high-quality DNA)
Product of Conception (POC) or (minimum 200mg of POC)
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