Chromosome Microarray Analysis: Information for Health Professionals

DNA from the sample is prepared and hybridized to a glass slide, on which a large number of molecular probes are arrayed; these probes consist of small segments of DNA corresponding to clinically significant (and potentially significant) regions covering the entire genome.  Currently available microarrays contain more than two million unique DNA probes.  Computerized analysis of the hybridization pattern on the slide reveals the number of copies of DNA corresponding to each probe location.  Therefore, this analysis is able to diagnose deletions and duplications of whole chromosomes, portions of chromosomes, and specific locations where copy number variants (CNVs) are associated with particular genetic diseases.

What types of disorders can chromosome microarray analysis diagnose?

• A chromosomal cause for a pregnancy loss, even when fetal tissue or products of conception does not contain viable cells
• The basis for fetal anomalies detected by ultrasound, when conventional chromosome analysis on a prenatal diagnosis sample was normal
• A genetic etiology for an infant, child, or adult who has mental retardation, with or without physical abnormalities and/or birth defects
• Microdeletion or microduplication syndromes that would not be detected on a routine prenatal diagnosis sample

• Microarray analysis detects unbalanced, but not balanced, chromosome abnormalities.  Thus, blood chromosome analysis for both members of a couple having recurrent pregnancy loss is still important.
• With some types of microarrays, additional genetic information can be obtained, including suspected consanguinity or uniparental disomy.
• Microarray analysis does not identify all genetic disorders.  For instance, it does not detect sequence variation (e.g., point mutations), a major cause of dominant, recessive, and X-linked disorders.
• Hundreds of small chromosome deletions and duplications are found in everyone; hence, the clinical significance of some CNVs identified by microarray analysis cannot be determined.  Parental microarray studies are sometimes necessary to properly interpret those "variants of uncertain clinical significance"; however, even then, the clinical significance of some abnormal results remains uncertain.

Genetic consultation can be helpful in ordering and interpreting microarray analysis, and may also identify an indication for additional genetic testing, based on clinical findings and family history, when determining a diagnosis.
 
 

Services | Insurance | Directions | Glossary | Genetics links | Topics of Interest | Our Staff  | Pictures | Contact us | Home