Prenatal Chromosome Studies
Amniotic fluid cytogenetic evaluation is appropriate for indications of advanced maternal age, abnormal ultrasound findings and other genetic concerns at 15-20 weeks gestation. Supply 15-25 ml of amniotic fluid in sterile 15 ml conical tubes. Please provide clinical indication and gestational age. Average turnaround time is 10-14 days.
Chorionic villus cytogenetic evaluation provides earlier detection of cytogenetic abnormalities at 10-13 weeks gestation. Supply 15-40 mg of villi in RPMI media along with clinical indication. Average turnaround time is 7-10 days.
Product of conception cytogenetic evaluation is appropriate in cases with multiple fetal losses or a suspected chromosomal cause of fetal loss/abnormalities. The ideal sample would include both chorionic villus and fetal tissue. Place sample in sterile mammalian culture medium i.e. RPMI or HEPES (if not available, contact lab for transport medium – do not immerse in saline). Average turnaround time is 2-4 weeks.
Perinatal/Pediatric/Reproductive Cytogenomic Studies
Genomic analysis using aCGH has been recommended as the first-tier genetic evaluation for pediatric patients with multiple congenital anomalies (MCA), dysmorphic features, failure to thrive (FTT), developmental delay (DD), unexplained mental retardation (MR) and autism spectrum disorders (ASD). Chromosome analysis will be performed for patients with a suspected chromosome syndrome (i.e. Down syndrome) or family history of a chromosome abnormality, primary or secondary amenorrhea, couples experiencing multiple pregnancy losses or infertility, etc.
Supply 3-7 ml of blood in sodium heparin vacutainer. Please provide clinical indication. Average turnaround time for aCGH is 2-4 weeks and for routine chromosome analysis is 5-7 days.
Cytogenetic analysis from skin biopsies is indicated for suspicion of mosaicism and cases such as Pallister-Killian syndrome. Ideal sample is a sterile punch biopsy including some dermal tissue. Place sample in sterile mammalian culture medium (if not available, contact lab for transport medium – do not immerse in saline). Please supply clinical indication. Average turnaround time is 2-4 weeks.
Hematologic Cytogenetic Studies
Bone marrow cytogenetic evaluation is considered appropriate for patients with neoplastic or pre-neoplastic hematological disorders. Supply 1-2 ml of bone marrow aspirate in sodium heparin vacutainer. Please supply clinical indication. Average turnaround time is 4-7 days (longer for B-/T-cell malignancies if mitogen stimulation is indicated).
Cytogenetic evaluation of lymph node, spleen, or solid tumor samples is appropriate in patients where neoplastic or pre-neoplastic cells are suspected to be present in the biopsied sample. Supply 0.3-1 cubic centimeter sample submerged in sterile culture medium (or a balanced salt solution). Please supply clinical indication. Turnaround time varies by specimen from 5 to 30 days.
Cytogenetic evaluation of unstimulated blood samples is appropriate in patients with acquired hematologic malignancy where sufficient neoplastic or pre-neoplastic cells (blast cells) are detected in peripheral blood. If the neoplasm is of lymphoid origin then stimulation is needed for B-cells (IL2/IL4) or T-cells (PHA). If the blast count or mitotic index is low in the blood, chromosome analysis may be infeasible and interphase FISH or aCGH could be an alternative. Supply 5-10 ml of peripheral blood in sodium heparin vacutainer. Please supply clinical indication. Average turnaround time is 4-7 days.
Fluorescence In Situ Hybridization (FISH) Testing
FISH testing extends routine cytogenetic banding methods by resolving ambiguous diagnoses and providing another tool to diagnose submicroscopic and cryptic abnormalities. FISH is a relatively simple, fast, and reliable procedure. FISH testing can be performed independently or concurrently with other cytogenetics studies.
Applications of FISH for hematologic disorders include delineation of chromosomal numerical abnormalities, detection of recurrent translocations and gene rearrangements, and determination of donor cell engraftment following sex-mismatched bone marrow and stem cell transplants. Disease-specific FISH panels for MDS, AML, B-ALL, CLL, MM/MGUS and lymphoma have been standardized to supplement routine chromosome analysis to screen for recurrent chromosome abnormalities.
Applications of FISH in constitutional abnormalities include detection of origin of marker chromosomes, delineation of subtle rearrangements, and confirmation of common microdeletion/duplication syndromes. Examples include Williams-Beuren syndrome (7q11.2 del), DiGeorge/Velocardiofacial/CATCH 22 (22q11.2 del), Prader Willi and Angelman syndromes (15q11.2 del), Smith Magenis (17p11.2 del), Miller-Diecker/Lissencephaly (17p13 del), STS/Steroid sulfatase/Ichthyosis and Kallman syndromes (Xp22.3 del), and XIST (Xq13) and SRY probes for X inactivation, sex reversal, and other sex chromosome abnormalities (e.g. Turner with marker).
Array Comparative Genomic Hybridization (aCGH) Analysis
aCGH analysis has been recommended as the first-tier genetic test for pediatric patients with DD/MR/MCA/ASD. It has been used for prenatal cases with suspected fetal anomalies and known structural chromosomal abnormalities, and also as a salvage procedure for products of conception or cancer cases with cell culture failure. Please contact the lab if aCGH analysis is required for cancer diagnostics.