Postnatal Chromosome Testing

Chromosome analysis involves the culturing of living cells. The harvested metaphase cells are stained (G-banding) and viewed under the microscope for numeric and structural abnormalities. The resolution for chromosome analysis is about 5-10Mb. The turnaround time is subject to growth variables and complexity of analysis. Results are generally available in approximately 2-3 weeks. Preliminary results on STAT cases to rule out trisomy are available in 48 hrs and are finalized within 7 days. Microscopic examination of both chromosome number and structure is performed. Examination of 20 metaphases is routinely performed and additional metaphases will be studied when indicated. At least 5 cells are fully analyzed with 3 or more G-banded karyograms created by computer image analysis on each patient.

Chromosome Analysis Options

  • Routine and stat peripheral blood chromosome analyses
  • High resolution peripheral blood chromosome analysis
  • Mosaicism study to rule out mosaic aneuploidy
  • Newborn cord blood chromosome analysis
  • 5-cell analysis in conjunction with microarray analysis

Chromosome analysis is the first line test for the following conditions:

  • Patient with suspected aneuploidy (Trisomy 13, Trisomy 18, Trisomy 21 or Down syndrome, Turner syndrome, Klinefelter syndrome)
  • Phenotypically normal individual with (or partner with) repeated pregnancy losses
  • Family history of chromosome rearrangement

Specimen Requirements

Postnatal And Adult Karyotyping And Fish
Specimen Types Requirements Turnaround Times
Peripheral Blood 1 green top tube (sodium heparin) containing 5 cc whole blood

For infant or young children:
1 green top tube (sodium heparin) containing 1-3 cc whole blood

If CGH testing is anticipated later 1 purple top tube (EDTA) containing 5cc whole blood is requested
2-3 weeks for routine cases

48 hr. verbal preliminary results on STAT analyses; 7 day final report on STAT analyses.
Postnatal And Adult (CGH Or CGH+SNP, FISH And KARYOTYPING)
Specimen Types Requirements Turnaround Times
Peripheral Blood 1 green top tube (sodium heparin) and one purple top tube (EDTA), each containing 5 cc whole blood

For infants or young children:
1 green top tube (sodium heparin) and one purple top tube (EDTA) , each containing 1-3 cc whole blood

Requirements Document and Requisition Form

Use Adobe Acrobat to print the PDF forms.

Advantages And Limitations

  • Conventional cytogenetic analysis is capable of detecting structural and numeric chromosomal abnormalities in postnatal samples with a resolution of 5-10 Mb (575 G-banded level for routine cases and 650 G-banded level or higher for high resolution cases).
  • Cryptic submicroscopic microdeletions and microduplications cannot be detected by conventional chromosome analysis.
  • Conventional cytogenetic analysis requires cell cultures for metaphase preparations.