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.
Types of Blood Tests
- 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
|Postnatal And Adult Karyotyping And Fish|
|Specimen Types||Requirements||Turnaround Times|
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
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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.