Constitutional Studies
Chromosome Analysis – Blood
Test Overview
CPT Code(s)
88230, 88262, 88280, 88291
Methodology
Culture / Microscopy / Karyotype
Specimen Requirements
Container: Sodium Heparin (green top tube)
Optimal Quantity: 4-5 ml
Minimum Quantity: 1-2 ml
Storage: Room Temperature
Stability at Room Temperature: 8 hours, then refrigerate
Transportation: Avoid freezing or heating over 35OC
Turnaround Time
STAT, including infants 6 months or younger: Preliminary results in 24 hours
Routine: Final report in 7-10 days for 90% cases
Test Detail
Clinical Significance
A chromosome analysis on peripheral blood may be clinically significant to identify genetic conditions associated with indications such as, developmental delay, failure to thrive, congenital anomalies, dysmorphic features, intellectual disability, ambiguous genitalia, short stature, multiple miscarriages and infertility. It may also be relevant in cases to confirm or exclude the diagnosis of known chromosomal syndromes.
Clinical Background
Chromosome analysis is the microscopic examination of chromosomes in the metaphase stage of the cell cycle. This type of analysis detects changes of the chromosome modal number and within the chromosome structure. These changes include trisomies (i.e. 21 or Down syndrome), monosomies (i.e. 45,X or Turner syndrome), deletions (complete breakage of a chromosome segment resulting in partial monosomy) and balanced or unbalanced translocations (chromosomal material from 2 or more chromosomes that has completely broken off and reunited onto another chromosome causing partial monosomies/trisomies and resulting in congenital syndromes, miscarriages and infertility). In some cases, the abnormalities only exist in a subset of cells, or mosaic background, and an increase in the number of metaphases examined is required to determine the percentage of cells representing the abnormality. Sometimes even the highest banding resolution cannot detect submicroscopic changes and a FISH study is required (i.e. DiGeorge, Prader-Willi and Angelman syndromes). Chromosome analysis on peripheral blood serves as a diagnostic study for multiple relevant genetic abnormalities in one test, whereas molecular studies are significant in cases where a diagnosis has been made or a suspicion exists and specific testing is targeted.
Methods
T-cells and B-cells from peripheral blood are stimulated using mitogens such as PHA and Lectin. Short term cultures are harvested at 24 and 72 hours for STAT cases and at 48 and 72 hours for routine cases, then G-banded.
Analysis and karyotyping is carried out by two certified technologists at high resolution from 550 or above band level, reviewed by the manager and reported by the director.
Interpretation of Results
The morphologic interpretation and correlation of results on all cases is performed by a board-certified doctoral level scientist (laboratory director). The final report identifies the chromosomal sex and modal chromosome number. If abnormalities are present, they are explained in a paragraph which helps to clarify and correlate chromosomal findings with phenotype. Genetic counseling is recommended when chromosome aberrations, mosaic conditions, or unusual results are found, along with recommendation for further testing (i.e. microarray). References are included in the report to help the referring physician with interpretation, which include books or journals that contain appropriate information.
Chromosome Analysis – Product of Conception
Test Overview
CPT Code(s)
88233, 88262, 88280, 88291
Methodology
Culture / Microscopy / Karyotype
Specimen Requirements
Placenta, umbilical cord, and internal fetal organs are all suitable for analysis. If possible, please send chorionic villi.
Container: Sterile, leak-proof containers with transport media or sterile saline (i.e. Hanks Balanced Salt Solution). Do not place in formalin.
Optimal Quantity: 1x1x1 cm of at least two fetal tissues, one being chorionic villi
Minimum Quantity: 1 fetal tissue
Storage: Room Temperature
Stability at Room Temperature: 8 hours, then refrigerate
Transportation: Avoid freezing or heating over 35OC
Turnaround Time
Final report in 14-28 days
Test Detail
Clinical Significance
Indications for cytogenetic analysis on products of conception (POC) include recurrent spontaneous abortions, abnormalities on ultrasound prior to pregnancy loss, intrauterine growth retardation, confirmation of abnormal prenatal results or pregnancy loss after IVF.
Clinical Background
Fetal tissues or extra embryonic membranes are frequently used to diagnose fetal chromosome abnormalities that are associated with approximately one-half of all first trimester spontaneous abortions. The most common chromosome abnormalities seen in spontaneous miscarriages are trisomy 16 and monosomy X. In some cases where the POC karyotype revealed a structural rearrangement, parental chromosome analysis is requested. The diagnosis of an abnormal karyotype in a POC may provide a chromosomal basis for the pregnancy loss. It may also help in clarifying the risk for future miscarriages or for the birth of a chromosomally abnormal child. Abnormal POC cytogenetic results may preclude the need for extensive infertility evaluation.
Methods
Tissues from products of conception are cultured to produce metaphase cells for G-banded chromosome analysis. Long term cultures are harvested at approximately 10-14 days, then G-banded. Analysis and karyotyping of 20 metaphases is routinely performed and additional metaphases will be studied when indicated.
Interpretation of Results
The morphologic interpretation and correlation of results on all cases is performed by a board-certified doctoral level scientist (laboratory director). The final report identifies the chromosomal sex and modal chromosome number. If abnormalities are present, they are explained in a paragraph which helps to clarify and correlate chromosomal findings with phenotype. Genetic counseling is recommended when chromosome aberrations, mosaic conditions, or unusual results are found, along with recommendation for further testing (i.e. microarray). References are included in the report to help the referring physician with interpretation, which include books or journals that contain appropriate information.
Chromosome Analysis – Amniotic Fluid
Test Overview
CPT Code(s)
88235, 88267, 88280, 88291
Methodology
Culture / Microscopy / Karyotype
Specimen Requirements
Container: Two 15 ml sterile leak-proof conical tubes (discard 1st milliliter to avoid maternal cell contamination)
Optimal Quantity: 20-25 ml
Minimum Quantity: 10 ml
Storage: Room Temperature
Stability at Room Temperature: 8 hours, then refrigerate
Transportation: Avoid freezing or heating over 35OC
Turnaround Time
Final report in 7-10 days for 90% cases
Test Detail
Clinical Significance
A chromosome analysis on amniotic fluid may be clinically significant to identify genetic conditions associated with indications such as, advanced maternal age (AMA), sonographic anomalies, suspicious for trisomy 13, 18 or 21, abnormal quad screen, abnormal MaterniT21, open neural tube defect (NTD), genetic abnormality carrier and previous child with chromosome abnormality. It is also relevant in cases to confirm a chromosome diagnosis by FISH and MaterniT21.
Clinical Background
Chromosome analysis on amniotic fluid is a procedure to rapidly culture and harvest amniocytes (amniotic cells) from amniocentesis for prenatal diagnosis of genetic and de novo (new or not genetic) chromosomal disorders. This type of analysis detects changes of the chromosome modal number, most often the common aneuploidies, and within the chromosome structure. Changes due to chromosome structure are usually associated with deletions or additions due to parent carrier status. Amniocytes are most viable when drawn by amniocentesis performed between 15 and 18 weeks gestation.
Methods
Amniotic fluid samples are long term cultures set up using the in situ method. If two tubes with fluid are received, two cultures are initiated, “A” and “B”. The cells are usually ready for harvest in about 7 days. Fifteen cells are counted and only one metaphase from each in situ colony is studied. Usually 8 cells from “A” culture is counted with 3 analyzed and 7 cells from “B” culture is counted with 2 analyzed, for a minimum of 5 completely analyzed metaphases. Abnormal cases may require analysis of additional cells which sometimes results in longer culturing time and turnaround time.
Interpretation of Results
The morphologic interpretation and correlation of results on all cases is performed by a board-certified doctoral level scientist (laboratory director). The final report identifies the chromosomal sex and modal chromosome number. If abnormalities are present, they are explained in a paragraph which helps to clarify and correlate chromosomal findings with phenotype. Genetic counseling is recommended when chromosome aberrations, mosaic conditions, or unusual results are found, along with recommendation for further testing (i.e. microarray). References are included in the report to help the referring physician with interpretation, which include books or journals that contain appropriate information.
AFP / AChE
Alpha-fetoprotein (AFP) is a screening test to detect developmental abnormalities in the fetus. An AFP test is usually requested with the chromosome analysis. When the AFP is elevated, it is automatically reflexed for acetylcholinesterase testing.
Chromosome Analysis – Skin
Test Overview
CPT Code(s)
88233, 88262, 88263, 88280, 88291
Methodology
Culture / Microscopy / Karyotype
Specimen Requirements
Container: Skin biopsies should be placed in sterile leak-proof containers with transport media.
If media is not available, place the specimen in sterile saline (e.g. Hanks Balanced Salt Solution).
Do not place in formalin.
Optimal Quantity: 1.0 cm2 or 2-3 punch biopsies
Storage: Room Temperature
Stability at Room Temperature: 8 hours, then refrigerate
Transportation: Avoid freezing or heating over 35OC
Turnaround Time
Final report in 14-28 days
Test Detail
Clinical Significance
A chromosome analysis on skin may be clinically significant to identify constitutional chromosome abnormalities observed in skin fibroblasts but not in peripheral blood lymphocytes (e.g. Pallister-Killian syndrome), to evaluate possible tissue-specific variation in patients with chromosomal abnormalities identified in peripheral blood lymphocytes and to confirm suspected mosaicismbased on skin pigmentation variation or a previous ambiguous karyotype.
Clinical Background
Although mosaicism for chromosome abnormalities in lymphocyte cultures is common, apparent restriction of mosaicism to one tissue is unusual. After examination of lymphocyte karyotypes, certain patients warrant cytogenetic evaluation of a second tissue, usually cultured skin fibroblasts. Cytogenetic analysis from skin biopsies is indicated when there is a suspicion of mosaicism(e.g. in Pallister-Killian syndrome), or when the physician deems that skin sampling is preferable for clinical reasons.
Methods
Skin tissues are cultured to produce metaphase cells for G-banded chromosome analysis. Long term cultures are harvested at approximately 10-14 days, then G-banded. The fibroblast cells are studied at approximately 400 – 500 band level using 20 metaphases with complete analysis of 5 metaphase cells and 2 karyotypes.
Interpretation of Results
The morphologic interpretation and correlation of results on all cases is performed by a board-certified doctoral level scientist (laboratory director). The final report identifies the chromosomal sex and modal chromosome number. If abnormalities are present, they are explained in a paragraph which helps to clarify and correlate chromosomal findings with phenotype. Genetic counseling is recommended when chromosome aberrations, mosaic conditions, or unusual results are found, along with recommendation for further testing (e.g. microarray). References are included in the report to help the referring physician with interpretation, which include books or journals that contain appropriate information.