Chromosomal microarray analysis (CMA) is method of choice for measuring gains and losses of DNA throughout the human genome. The results are expressed as Copy Number Variants (CNVs) as pathogenic, non-pathogenic or variant of unknown significance (VOUS). CNVs are defined as duplicated or deleted segments of DNA of at least 1000 base pairs (1 Kb) in size with difference from reference genome.

Microarray Can identify:

1. Chromosomal Aneuploidy (all 23 pairs of chromosomes)
 
2. Submicroscopic Chromosome abnormalities (including clinically relevant pathogenic microdeletion & microduplication syndromes)
 
3. Large changes in the structure of Chromosomes

CNVs obtained in microarray findings and are expressed as

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1. Pathogenic: CNV of clinical significance detected; 15% genetic disease burden.
 
2. Nonpathogenic: CNV of no clinical significance.
 
3. Variants of uncertain significance (VOUS): CNV of uncertain significance

Advantages: Microarray analysis

1. NO CULTURE FAILURES: DNA can be obtained from uncultured specimen does not require actively dividing cells, results usually available more quickly than karyotyping which require cultured cells.
 
2. HIGHER RESOLUTION: Chromosome microarray yields more genetic information because of its higher resolution(10-400Kb) and can detect higher rate of results compared to karyotyping (5-10 MB).
 
3. NO MATERNAL CONTAIMINATION: Single Nucleotide Polymorphism (SNP) based microarray analysis can detect triploidy and also identifies maternal cell contamination thus decreasing false negative results
 
4. HIGH DIGNAOSTICS YEILD: Chromosome microarray analysis identifies additional clinically (4-6%) significant abnormalities in cases of abnormal ultrasonography abnormalities with normal conventional karyotype results
 
5. ACCURATE:Due to AUTOMATION in microarray No Interpersonal Observer Variation in results

Limitations: Microarray analysis