Postnatal Chromosome Analysis

Chromosome Analysis

Blood, Products of Conception, Cordocentesis

Chromosome analysis is performed on peripheral blood, cord blood, products of conception or skin biopsy specimens from individuals suspected of having a chromosome abnormality.

WHO SHOULD BE OFFERED CHROMOSOMAL ANALYSIS?

  • Couples experiencing infertility or 2 or more unexplained pregnancy losses or perinatal deaths (about 6% have a chromosomal abnormality)
  • Products of conception or skin biopsies of fetal tissues from unexplained fetal losses
  • Newborns with serious anomalies or three or more minor congenital abnormalities
  • Newborns with ambiguous genitalia, small penis, or hypospadius
  • Infants and children with developmental delays or unexplained mental retardation, learning disabilities or behavioral problems
  • Individuals with Down syndrome, Fragile X, autism, DiGeorge, Prader-Willi, Angelman, and Smith-Magenis
  • Females with inguinal hernia, primary or secondary amenorrhea, and/or proportional short stature
  • Females with premature ovarian failure
  • Males with oligospermia or azoospermia, because 5-14% have a chromosomal abnormality, including balanced translocations. All males seeking assisted reproductive technologies
  • Males with small testes or gynecomastia
  • Blood relatives of individuals with a structural chromosomal abnormality

WHAT OTHER TESTING SHOULD BE PERFORMED ON SPECIMENS?

Fluorescence in situ hybridization (FISH) microdeletion analysis is a molecular test which uses DNA probes to detect the presence or absence of specific chromosome regions. Many chromosome deletions are so small (micro) they cannot be detected by chromosomal analysis alone.

GeneCare provides the full range of DNA to detect chromosomal abnormalities including the following microdeletion syndromes can be detected by FISH analysis: Angelman, DiGeorge/Velo-Cardio-Facial (Shprintzen), Miller-Dieker/Lissencephaly, Prader-Willi, Smith-Magenis, Williams, X-linked Ichthyosis (Steroid Sulphatase Deficiency) /Kallmann. Please inquire about other microdeletion syndromes.

Special chromosome banding, FISH (paint, centromere, and subtelomere) and DNA probe analysis are used to identify small marker chromosomes and structural rearrangements.

Subtelomere analysis should be considered for patients with unexplained mental retardation, autism, developmental delay, learning disabilities, congenital anomalies or recurrent pregnancy losses. Subtelomeric alterations near the end of a chromosome account for About 7-8% of unexplained moderate to severe mental retardation and 0.5% of mild MR patients with normal chromosomal analysis. A subtelomere alteration will not be seen by routine or high resolution chromosomal analysis. These alterations can be detected using special FISH probes. About 50% of unbalanced telomere rearrangements are inherited, which suggest a high recurrence risk.

PCR analysis, Southern analysis for direct DNA or linkage analysis and comparative genome hybridization are also available.

SPECIMEN COLLECTION AND TRANSPORT

  • Call GeneCare at (800) 277-4363 for consult and questions about testing or transport
  • Complete Lab Requisition Form
  • Label each specimen tube with patient name, birth date and collection date
  • Transport by courier or PRIORITY OVERNIGHT including specimens for Saturday Delivery by Federal Express
  • Please notify our Center of specimen collection and transport to insure successful delivery. Specimens are accepted 7 days a week.

SPECIMEN REQUIREMENTS

  • BLOOD: Draw 1-10 ml peripheral vein, cord, or cardiac (less than 12 hours after fetal death) blood into a sodium heparin (200 units) vacutainer or plastic BD syringe. Blood drawn in syringe should be gently transferred to green top (Na Heparin) vacutainer for transport. Patients should avoid fatty foods and alcohol 12 hours before blood draw.

 

  • SKIN, CORD, AMNION, OR CHORION: For fetal deaths, stillborns and neonatal deaths, obtain cord, skin and blood immediately. Call our Center for free tissue culture media or draw a 10 ml red top vacutainer from mother or other person, spin and remove serum with sterile syringe and needle and transfer to another sterile tube. Aseptically obtain cord, amnion, chorion and villi samples. Place in a serum tube. If the fetus is not macerated, obtain 10 mm sterile (alcohol wipe) skin dermis and tendon biopsy from above the knee using a sterile needle and scalpel. If the biopsy is not sterile, shake biopsy vigorously in saline in a closed sterile tube. Transfer biopsy to the maternal serum or Hank's solution tube. Refrigerate until transported. Do not freeze.

TURNAROUND TIME (Avg.)

Blood Chromosome

5 days

STAT Blood

48 hours

POC / Skin

8 days

DNA Testing

7 days

Interphase FISH

24-48 hours

Microdeletion FISH

7 days

RESULT REPORTING

GeneCare promptly reports results by telephone, fax, and/or mail. All abnormal results are promptly telephoned to the designated contact by one of our medical staff.

Information provided on this site is for information purposes ONLY.  This should not be used as a substitute for professional medical advice, treatment or diagnosis.