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Test Code Billings Clinic: 8752 Chromosome Analysis, Amniotic Fluid

Performing Laboratory

Shodair Children's Hospital, Helena, Montana

Useful For

  • This test will provide a fetal karyotype allowing for the prenatal detection of chromosome abnormalities such as trisomy 21.
  • Fetal loss rate is considered to be 0.5% at 14 to 18 week sampling and 2% to 3% at 10 to 14 week sampling. Cultured cells can also be tested using other methods for the prenatal diagnosis of genetic diseases. AFP testing is performed on all amniotic fluid samples.
  • Testing may be appropriate for women who are 35 years of age or older, have a family history of a chromosome abnormality, have an abnormal fetal ultrasound, have a positive maternal serum marker screen, have a history of spontaneous abortions or a previous child with multiple congenital abnormalities.

Methodology

  • G-Banded chromosomes of 15-20 mitotic cells are examined from in situ cultures.
  • Rarely culture failure can result. Reasons for culture failure include lack of amniocytes in the fluid and contamination of the fluid with bacteria or yeast.

Specimen Requirements

  • 20 mL to 25 mL of amniotic fluid in a screw-capped, sterile culture tube(s).
  • Bloody specimen is undesirable.
  • Maintain sterility and forward promptly at ambient temperature only.
  • Specimen cannot be frozen or refrigerated.
  • Wrap specimen in foil to protect from light.
  • Please complete a “Prenatal Referral Form” indicating patient’s name, date of birth, sex, physician’s name, referring diagnosis, relevant family history, last menstrual period (LMP), estimated duration of pregnancy by ultrasound, and date of ultrasound.

Reference Values

Reference values are included with patient’s report.

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

88235 - Tissue culture for non-neoplastic disorders; amniotic fluid or chorionic villus cells
88269 - Amnio cell analysis
88280 - Chromosome analysis; additional karyotypes, each study