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Cytogenetics Laboratory

Same-Day FISH:

If the CVS or amniocentesis procedure is performed in the morning, results of the FISH analysis are usually available on the same day. FISH is a laboratory method used to get rapid results for the chromosome abnormalities that we are most concerned about. FISH tests for the most common chromosome abnormalities, including Down syndrome, trisomy 18, trisomy 13, as well as sex chromosome abnormalities and fetal gender.

Karyotyping:

A full chromosome analysis, called a ‘karyotype’, is currently considered to be the standard of care for pregnancies undergoing prenatal diagnosis for chromosome abnormalities, and is therefore required for all CVS and amniocentesis samples. The karyotype is a way of looking at each chromosome pair in multiple cells obtained from a pregnancy. It involves preparing and looking at cells under a microscope. Because of the preparation involved, the test usually takes about two business weeks following the procedure. Patients will be called with this result as soon as the final karyotype is complete.

Chromosome Microarray:

In addition to standard chromosome analysis, there is a new type of testing that may be performed on the CVS or amniocentesis sample, called prenatal chromosome microarray (CMA). Microarray analysis has the ability to find smaller chromosome changes compared to conventional karyotyping.

A recent joint opinion issued by the American College of Obstetricians and Gynecologists and the Society for Maternal Fetal Medicine (Obstetrics and Gynecology 122:1374, 2013) recommended the use of CMA for prenatal diagnosis because of its capacity to identify chromosome abnormalities that are too small to be detected by conventional karyotyping. Insight Medical Genetics is now applying CMA to the accelerated confirmation of results obtained by FISH following an invasive procedure and to the analysis of CVS and amniocentesis samples obtained following either a negative finding for aneuploidy by FISH or the observation of an abnormal ultrasound finding. All microarray analyses will also be accompanied by a 5 cell karyotype to determine the presence of translocations or possible mosaicism.

The Insight Medical Genetics microarray panel includes approximately 80 known genetic syndromes, including nearly all currently understood microdeletion and microduplication syndromes. These genetic syndromes are very different from one another, but are important because they are known to cause significant problems, including birth defects, developmental disabilities, and/or intellectual disabilities. In addition, other deletions and duplications above a 1 MB threshold are investigated for possible reported abnormalities.

Molecular Genetics Laboratory