Microarray
Approximate time required for this test:
1-2 weeks
Sequencing
Unlike the other tests described here, a microarray is a ‘gene chip’ based test, not a sequencing test. A microarray is a microchip covered in tiny spots containing probes that bind with a specific DNA sequence in the patient’s DNA sample. Two types of chromosomal microarray are SNP arrays and CGH arrays.
Analysis
Fluorescent labels on the DNA are used to visualise the results. The intensity of fluorescence shows how much of the patient’s DNA is bound, in comparison to a reference DNA sample. The test can identify normal, increased (gain) or decreased (loss) amounts of genetic material in the patient’s DNA.
Variant identification & interpretation
Microarray detects: aneuploidy - or changes in whole chromosome number; structural variants - large scale chromosomal changes such as deletions, insertions, duplications; copy number variants (CNVs) - smaller gains or losses of one or several genes or regions of a chromosome. Microarray does not detect single nucleotide changes, small deletions and duplications, triplet repeat sequences or balanced chromosomal rearrangements.
Case review / Medical scientist
Variants identified by chromosomal microarray tests are reviewed against the clinical information and patient phenotype. Variants that may explain the phenotype and clinical features are curated, interpreted and reported by the medical scientist.