How to send sample for genetic test
Contributed by Dr Seema Thakur
Senior Consultant genetics,
Apollo & Fortis Hospital
How to collect POC sample for genetic tests
| ꜜ |
Samples taken before suction, by dilatation and curettage.
In medium/ sterile NS
Add a drop of gentamycin
(50ug/ml) & heparin |
|
| ꜜ |
Cord blood in heparin /EDTA vaccutainer
Placenta, ,Fetal skin- in media or sterile NS
Add a drop of gentamycin
(50ug/ml) & heparin |
|
Flow chart 1: This chart briefly describes how POC sample should be collected
Figure 1A: The figure shows that collection of placenta for genetic testing should be done from the point where cord joins the placental tissue. Cut it equivalent to the size of one rupee coin.
|
 |
EDTA vacutainer
(blood sample collection
for DNA based test)
|
Heparin vacutainer
(blood sample collection for
karyotype / FISH based test) |
| S.No. |
Test |
Technique |
Turn around time |
Cost |
| 1. |
Karyotyping |
Culturing of fetal cells requires dividing cells that are harvested at metaphase and karyotyping is done using microscope limiting the resolution to 5Mb |
3-4weeks |
7-10K |
| 2. |
FISH |
Uses fluorescent probes that binds only to the targeted regions of the chromosome with a high degree of sequence complementarity and is thus limited being able to determine specific chromosomal aberrations that are targeted
|
3-5 days
|
5-10K
|
| 3. |
BoBs(Bacterial artificial chromosome On Beads) |
The probes are designed to detect aneuploidy in all chromosomes by quantifying proximal and terminal regions of each chromosomal arm in addition to commonly known microdeletions
|
1 week |
8-10K |
| 4. |
Microarray (CGHarray, SNParray) |
The probes are used for analysing copy number variations (CNVs)and single nucleotide polymorphisms (SNPs) relative to a reference sample, without the need for culturing cells. It offers a resolution of 10Kb to 1Mb depending on the array used |
7-15 days |
7-50K |
| 5. |
Exome/whole genome sequencing |
DNA samples are fragmented and biotinylated oligonucleotide probes are used to selectively hybridize to target regions in the coding region or entire genome. The sample is then sequenced before proceeding to bioinformatic analysis. It can depict single nucleotide changes, thus offers highest resolution |
2-4 weeks |
20-50K |