Quantitative fluorescent-polymerase chain reaction (QF-PCR) enables the rapid detection of both the common aneuploidy syndromes (Trisomy 21, Trisomy 18, Trisomy 13) and sex chromosome aneuploidies using DNA extracted from amniotic fluid, CVS, blood or solid tissue.
QF-PCR for the rapid detection of aneuploidy is used extensively throughout the UK and Europe. Test failure is rare (published data suggests 0.1%) and an uninformative result for one or more chromosomes is seen in only 0.4% of cases.
Polymorphic microsatellite markers located on the X and Y chromosomes and chromosomes 13, 18 and 21 are amplified by PCR and the amount of product quantified using software. The quantity of amplified product detected enables the total number of the targeted chromosomes present to be determined. While QF-PCR can be carried out on any tissue it is most widely used to provide rapid aneuploidy results on prenatal and neonatal blood samples.
A minimum of four polymorphic microsatellite markers are amplified from each target chromosome and all abnormal results are backed up using a second independent test; either a different set of polymorphic markers or interphase FISH. In the rare case where the QF-PCR result is uninformative, FISH testing will be carried out.
QF-PCR has the added advantage of being able to detect maternal cell contamination in amniotic fluid and chorionic villi samples.
WRGL also utilises QF-PCR on tissue samples if the cell cultures fail to grow.
|QF-PCR||$373||Amniotic fluid 10-20 ml
CVS 10-30 mg clean villi
For blood stained samples, 4 ml whole blood in EDTA (purple top) from the mother
Paediatric: 0-6mths 1-2 ml whole blood in lithium heparin (LH) tube (green top)
Solid tissue: unfixed sample transported in sterile tissue culture media