Chromosomal microarray (CMA) is a powerful cytogenomic tool for detecting subtle gains of DNA as small as 400 kb and losses of DNA as small as 200 kb. CMA can detect abnormalities in known microdeletion and microduplication syndrome regions, as well as submicroscopic abnormalities that may be missed by
standard and
high resolution chromosome analysis.
Features of the 180K CMA
- High resolution array containing 180,000 oligonucleotide clones
- Follows the International Standard Cytogenomic Arrays (ISCA) consortium guidelines for chip design
- Clones are spaced ~16 kb along the backbone
- Increased coverage in disease regions
- Targeted coverage of 500+ disease genes, microdeletion/microduplication syndrome regions, and subtelomeres
- Abnormalities detected at a resolution of 100-200 kb
- Two different software platforms available for analysis to increase overall accuracy and for quality control
- Confirmation studies, as well as parental FISH studies, performed on abnormal cases
Indications
CMA on tissue is performed to evaluate a pregnancy loss for small gains or losses undetectable by chromosome analysis.
Methodology
CMA involves extraction of fetal DNA from a tissue sample, labeling of the DNA, and hybridization to the CytoChip oligo microarray. A laser scanner detects the signal from the CMA slide, and interprets gains and losses relative to a normal control DNA using BlueFuse software. The CMA assay performs a comparison between the patient and control to confirm any gains or losses. Finally, FISH analysis is performed, if necessary, to confirm the abnormality detected.
Limitations
CMA will not detect balanced rearrangements (i.e., inversions, translocations) or very low level mosaicism. It will also not detect single gene mutations or single nucleotide mutations/polymorphisms. Abnormalities that are smaller than the resolution of the array also may not be detected.
If clinically relevant, common aneuploidies, such as Down syndrome or Trisomy 18, should be ruled out by chromosome analysis or fluorescence in situ hybridization before CMA testing is pursued.
Specimen Requirements
Submit 3-5 mm3 fetal tissue in a sterile, plastic, screw-top tube filled with sterile transport media. CGL can provide this media.
Hold at room temperature; refrigerate if overnight.
At this time, we are unable to accept products of conception or placental tissues where there is concern for maternal cell contamination.
Samples must be accompanied by a completed
Test Request Form. Indicate chromosomal microarray testing in the "Prenatal and Tissue Specimens" section, and include all pertinent medical and family history.