Additional Information

OGM Optical Genome Mapping (OGM) is designed to identify structural rearrangements (example: balanced and unbalanced translocations, gene fusions, and inversions), gains and/or losses of DNA content, as well as large regions of homozygosity (ROH). This represents a targeted assay that is based on the differential diagnosis and the recurrent clonal aberrations known to be associated with particular disorders. Genomic alterations that occur outside of the targeted regions may not be reported. Limitations:  OGM will not detect sequence level variants, imbalances involving regions not covered by probes, and is limited in its ability to detect variants involving repetitive elements around centromeres and telomeres. The lower limit of detection for aneuploidy, small copy number changes (25-500kb in size), and structural rearrangements is an ~10% variant allele fraction (VAF). Large copy number changes (>500 kb in size) with VAFs under 15% may not be reported. Copy neutral ROH involving a whole chromosome or chromosome arm may be reported; however, this assay is limited in its ability to detect low level mosaic copy neutral ROH. Failure to detect an alteration at any locus does not exclude the diagnosis of any disorder represented on OGM. At times it may not be possible to distinguish whether findings represent a clonal or constitutional finding.  If there is concern for a constitutional finding additional testing should be ordered on a sample free of disease.