Down syndrome is the most common aneuploides seen in live born babies with the prevalence of 1 in 1000 followed by other trisomies. The burden of aneuploides can be reduced with new molecular cytogenetic technology which helps in early intervention and genetic counselling. As our centre is being a referral centre for all genetic disorders, we receive a high risk couples related to chromosomal abnormalities as having one affected child. Since we are providing QF-PCR as a stand-alone test for postnatal diagnosis, the same methodology was extrapolated for prenatal diagnosis.
Initially, 500 postnatal samples (Blood in EDTA vial) and 240 amniotic fluid samples were received for analysis of chromosomal aneuploidies from various part of the country. The DNA was extracted with QIAamp DNA mini kit by Qiagen. QF-PCR was carried out with the following markers D21S1411, D21S11, D21S1435, D21S1412, AMEL, SRY, D18S535, D18S391, D13S258, D13S634 and XHPRT, X22 whose heterozygosity have been studied.
We observed 100% concordance with the clinical diagnosis as well as cytogenetic analysis of postnatal samples. With these results we went for prenatal services were chromosomal studies are very common for suspected Down syndrome pregnancies. Out of 240 pregnancies studied, 2% (5) was of Trisomy 21 and a single case of Trisomy 18 was identified, these results were also reconfirmed with karyotyping results.
Results of present investigation reassure QF-PCR as stand-alone test for high risk pregnancies. This is the first study from India that tested the in-house developed multiplex QF-PCR for post and prenatal diagnosis.