QF-PCR is the abbreviation for quantitative fluorescent polymerase chain reaction.
Results for ongoing prenatal referrals are reported within 5 days. Results for referrals from fetal tissues/productions of conception are reported within 15 days.
QF-PCR is a molecular technique used for diagnosis of the viable aneuploidies: trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome), trisomy 21 (Down syndrome). It can also detect Monosomy X (Turner syndrome) and triploidy and determine the fetal sex.
The test is employed at CHL to detect the common aneuploidies in fetal DNA, primarily prior to microarray or G-banded karyotyping.
While the test shares many similarities with rapid aneuploidy FISH, QF-PCR has the added benefit of genotyping the sample, which can help resolve mixed cell populations, identify maternal cell contamination, mosaicism, twin pregnancy and chimerism.
If the QF-PCR yields a normal result, a microarray (or karyotype if requested) may be performed.
Indications for QF-PCR +microaray:
• Ongoing pregnancy with increased risk of abnormality by maternal serum screen or NIPS
• Ongoing pregnancy with increased NT measurement (>3.5mm)
• Abnormalities on ultrasound or abnormal fetal phenotype
• One of the parents has a known chromosome rearrangement (eg. translocation)
• Recurrent miscarriage (defined as ≥ 3)
• Chromosome abnormality identified by G-banded karyotype
Genetics - Cytogenetics
Appropriate counselling where the implications for the microarray test and the expected results can be discussed. Completion of a specific patient consent form prior to ordering a microarray. Patient information leaflet and consent forms are available by searching Consent for Prenatal Microarray Testing in Sharepoint.
Include relevant clinical information, gestational age, mother's NHI# and fetal sex (if known) on request form.
Sterile specimen, MUST NOT not be in formalin. Can be with/without RPMI Tissue Transport Medium (order from CHL Patient and Client services 03 364 0484, open 09.00-17.00, Mon-Fri.
Products of Conception (POC) and Placenta - placental villi or recognisable fetal tissue (approx. 0.5 x 0.5cm). Please also send 2ml EDTA (purple top) blood from the mother for maternal cell exclusion testing and send together with the POC. A paternal specimen is usually not necessary and will be requested if required.
Fetal Tissue (post mortem) - Cartilage and placental villi are preferable. Please identify the tissues clearly on the request form. Spleen, liver or skin is not generally suitable for microarray testing.
Fetal Blood - 1-2mls (2-3 paediatric tubes)
Ambient (8 - 24 degrees Celsius)
Send without delay ambient
DO NOT FREEZE. DO NOT EXPOSE TO FORMALIN.
Comment in the report
Comment in the report
QF-PCR selectively amplifies certain regions of genomic DNA using fluorescently-labelled primers which bind to specific regions of chromosomes 13, 18, 21, X and Y. QF-PCR products are run on a capillary electrophoresis system and separated by size, so that each peak is the product of the amplification of a specific probe. The fluorescent signal intensity is measured digitally to determine the copy number for each target sequence.
Multiplex QF-PCR analysis is performed using the Elucigene QST*R plus v2 kit. PCR products are analysed using an ABI3500 genetic analyser and GeneMapper software. At least two informative STRs are required to interpret a result as abnormal.
QF-PCR will not detect balanced structural rearrangements or distinguish between aneuploidy caused by a nondisjunction event or an unbalanced rearrangement. QF-PCR can identify 20-30% of cases with mosaicism, which is comparable to karyotyping and FISH.
In 5-10% of specimens no result will possible, due to the presence of significant maternal cell contamination, poor fetal DNA quality or where no clearly identifiable villi or fetal tissue is detected. In these cases, no further testing will be initiated.
If aneuploidy or triploidy is detected, microarray testing will not be performed.