Cytogenetic studies, of normal versus abnormal chromosomes, are essential to the diagnosis and treatment of many diseases.
- Amniotic chromosome analysis – Prenatal diagnosis of chromosome abnormalities.
- Blood chromosome analysis – Detection of chromosomal abnormalities in patients with congenital anomalies, infertility and failure to thrive.
- Oncology chromosome analysis – Assists in diagnosis/classification/evaluation/monitoring of certain malignant hematological disorders.
- Tissue chromosome analysis – Diagnoses chromosomal causes for fetal death and determines recurrent risk for future pregnancy losses.
FISH (fluorescent in situ hybridization)
Fluorescent in situ hybridization (FISH) examines chromosomes on the DNA level. It is used to look at small and very specific segments of the DNA strand to see if each is present or absent. FISH studies are used to search for a very specific abnormality. These studies complement chromosome studies in providing valuable information.
- AneuVysion® – Identifies and enumerates critical chromosomes from amniotic fluid in high-risk pregnancies.
- Angelman – Detects micro-deletions of chromosome 15 associated with Angelman syndrome.
- BCR-ABL – Identifies and monitors the Philadelphia chromosome in patients with CML (chronic myelogenous leukemia), ALL (acute lymphoblastic leukemia), or AML (acute myelogenous leukemia).
- CLL Panel – Detects deletions/duplications in chromosomes associated with CLL (chronic lymphocytic leukemia).
- HER-2/neu – Adjunct testing to aid in diagnosis and treatment of certain breast cancers.
- Inverted 16 – Aids in the classification/evaluation/monitoring of a certain AML.
- Miller-Dieker Syndrome – Detects micro-deletions of chromosome 17 associated with Miller-Dieker Syndrome.
- Prader-Willi Syndrome – Detects micro-deletions of chromosome 15 associated with Prader-Willi Syndrome.
- RARA – Used in the classification/evaluation/monitoring of a certain AML.
- Shprintzen/DiGeorge – Detects micro-deletions of chromosome 22 associated with Shprintzen/DiGeorge Syndrome.
- Smith-Magenis – Detects micro-deletions of chromosome 17 associated with Smith-Magenis Syndrome.
- Sotos Syndrome – Detects micro-deletions of chromosome 5 associated with Sotos Syndrome.
- SRY – Aids in the diagnosis of a deletion/duplication in the sex-determining region of the Y chromosome.
- Subtelomere – Detects micro-deletions of the terminal portions of certain chromosomes.
- Williams Syndrome – Detects micro-deletions of chromosome 7 associated with Williams Syndrome.
AneuVysion® is a registered trademark of Abbott Laboratories.
CMA (chromosomal microarray analysis)
CMA is a revolutionary method of analyzing chromosomes for a large number of genetic disorders. It uses array-based Comparative Genomic Hybridization (aCGH) with approximately 180,000 oligos covering the entire genome. Genomic DNA from the test sample and a control sample are differentially labeled with fluorescent dyes and hybridized to the oligos. Results are analyzed using quantitative imaging methods and analytical software to assist in identifying each targeted DNA sequence as loss of copy number (deletion), gain of copy number (duplication) or normal copy number.
Chromosomal microarray analysis may be ordered for all patients with any indication of genomic imbalance, including:
- Dysmorphic features
- Unexplained mental retardation/developmental delay
- Autism spectrum disorder
- Multiple congenital anomalies
It is the more appropriate test for patients who are candidates for subtelomere FISH or multiple individual FISH tests. CMA is well suited for the detection of interstitial duplications that previously could only be detected by interphase FISH. Although CMA can detect some deletions or duplications that cause single-gene or continuous-gene phenotypes, additional testing methodologies should be appropriately considered.
A note about test limitations
CMA is a new and sensitive test. It is possible that the test will detect a genetic abnormality for which there is currently very little medical information that can predict the clinical problems that may develop in an individual. While the test is very accurate, not every genomic abnormality (genetic defect) can be detected by a test.
For some conditions, genomic gains or losses at a particular locus may represent only a certain percentage of the genetic changes associated with that given disorder. For instance, with respect to some disorders, 99 percent of the cases may be detected by the test, while for other disorders, the detection rate may be 70 percent or less. There are some changes in chromosomes that CMA cannot detect, such as balanced rearrangements or changes in regions not covered by the array. Many of these changes can be detected by karyotype analysis, which can be run as a supplemental test.