upmc   PITTSBURGH CYTOGENETICS LABORATORY

 

LABORATORY SERVICES

 

PRENATAL CHROMOSOME TESTING

Click to zoomCLINICAL INDICATIONS FOR CHROMOSOME ANALYSIS

SAMPLES FOR PRENATAL CHROMOSOME DIAGNOSIS

CHROMOSOME ANALYSIS OF AMNIOTIC FLUID

Chromosome analysis of amniotic fluid involves a short-term culture of specimens to provide an optimal number of metaphase cells for determination of chromosomal abnormalities. Microscopic examination of both chromosome number and structure is performed. Analysis of 20 metaphases, or 15 clones if available, is routinely performed and additional metaphases will be studied when indicated. Two or more G-banded karyotypes are created by computer image analysis on each patient.

CHROMOSOME ANALYSIS OF CHORIONIC VILLUS SAMPLING

This test, requiring chorionic villus sampling, is an alternative to genetic amniocentesis, and should be offered to women over age 34 years at conception. Chorionic villus sampling is usually performed at 10-12 weeks of gestation and provides earlier prenatal diagnosis than conventional amniocentesis. Cells are cultured until an adequate number are available for analysis. Microscopic examination of both chromosome number and structure is performed. Analysis of 20 metaphases is routinely performed and additional metaphases will be studied when indicated. Two or more G-banded karyograms are created by computer image analysis on each patient. Cells may also be cultured and sent to reference laboratories for DNA or Biochemical analysis for specific disorders if required.

Turnaround time varies from 7-14 days depending on cell growth and extent of workup, with an average of 10 days.

PRENATAL DIAGNOSIS (K-type and AneuVysion FISH)
Specimen Types Requirements
Chorionic villi Amniotic Fluid Minimum 10-15 mg of chorionic villus tissue in a sterile tube containing culture medium, sterile saline or balanced salt solution

Minimum 20cc of the fluid

 

SPECIMEN REQUIREMENTS (PDF TABLE)

CONSITUTIONAL STUDY REQUISITION FORM (PDF TABLE)

ADVANTAGES AND LIMITATIONS

Conventional cytogenetic analysis is capable of detecting structural and numerical chromosomal abnormalities in prenatal samples at the 450 G-banded level. Cryptic imbalances including microdeletions and microduplications cannot be detected by conventional chromosome analysis. In addition, conventional cytogenetic analysis requires dividing cells for metaphase preparation.