Cytogenetics

Chromosome Analysis Laboratory studies request form | CPT Codes/Price List (PDF)

Chromosome analysis is an important component in the diagnosis and evaluation of genetic disorders. Chromosome abnormalities in which there is too much or too little genetic material can result in congenital malformations, mental retardation, or aberrant sexual differentiation.

Chromosome disorders occur in approximately 1 in 150 liveborns and are a significant cause of mental retardation and dysmorphic features. In addition, over 50% of first trimester spontaneous abortions are due to a fetal chromosome abnormality. Chromosome analysis is indicated in the following cases:

Individuals with

suspected classic chromosomal syndrome
mental retardation of undetermined etiology
dysmorphic features
multiple congenital abnormalities
abnormalities of sexual development
ambiguous genitalia
pubertal failure
abnormalities of growth
certain types of malignancies

Couples with

two or more spontaneous abortions
infertility

Family members when

both parents of a child with a structural chromosome rearrangement, deletion, or duplication
all family members at risk of having a chromosome rearrangement

Pregnancy products of

abortuses (including blighted ova and missed abortions)
malformed stillborns
stillborns of undetermined etiology

Chromosome analysis can be performed on blood, solid tissue, bone marrow, amniotic fluid cells, and chorionic villi. The following sections describe the samples needed for specific types of chromosome studies.

Prenatal Chromosome Analysis (amniotic fluid, chorionic villus sampling)
Fluorescence In Situ Hybridization [FISH] (trisomy detection and sex determination, oncology, amniotic fluid, newborn screening, telomere alteration)
Cytogenetic Analysis of Leukemia (bone marrow, unstimulated leukemic blood)
Peripheral Blood Analysis (routine and high resolution)
Solid Tissue Analysis (skin biopsy, products of conception, abortus tissue)
Special Stains
CGH-Oligo Microarray

Additional Studies

Buccal Smear for Barr Body Analysis - FISH analysis for sex chromosome constitution is now preferred over buccal smear analysis. It is recommended that FISH analysis be followed by a G-banded chromosome study to confirm the results and to look for changes in chromosome structure that may go undetected by FISH.
Chromosome Breakage - certain conditions, such as Fanconi anemia, show an increased frequency of spontaneous chromosome breakage. In these cases, chromosome breakage studies are performed by treating cultured cells with mitomycin-C or diepoxybutane (DEB) to induce breakage. Chromosome breakage studies are not performed at GGC, but we can provide information about where to send samples for these special studies.
Sister Chromatid Exchange (SCE) represents the interchange of homologous segments between two chromatids of one chromosome. SCEs can be detected by growing cells under special culture conditions to produce differential staining of sister chromatids. SCE analysis aids in the diagnosis of inherited conditions such as Bloom syndrome, which shows an increased rate of SCE compared to controls. Because special culture conditions are required, chromosome breakage studies must be specifically requested.