New genetic testing service provides rapid and effective prenatal diagnosis

September 27, 2001

N.B. Please note that if you are outside North America the embargo for Lancet press material is 0001 hours UK time Friday 28th September 2001.

The first implementation of a new genetic testing service in the south-east region of the UK National Health Service (NHS) has resulted in the rapid diagnosis of fetal genetic abnormalities and early reassurance for pregnant women with normal test results, report authors of a study in this week's issue of THE LANCET.

Pregnant women are routinely offered an invasive prenatal test for chromosome abnormalities (such as trisomy 21, associated with Down's syndrome) if they are identified as being at high risk (eg. as a result of indications from blood or ultrasound tests, increased maternal age, or family history of chromosome abnormalities). Consequently, around 40 000 women a year in the UK NHS are given full chromosome assessment (karyotype analysis), which identifies genetic abnormalities in around 7% of fetuses. However, women have to wait for around two weeks for karyotype results, with implications for the decision to continue or terminate pregnancy. A different testing procedure, quantitative fluorescence (QF) polymerase chain reaction (PCR), has been shown to provide a rapid and effective analysis of autosomal trisomies (abnormalities characterised by the presence of an extra chromosome), which account for around 80% of all prenatal genetic abnormalities.

Caroline Ogilvie, Kathy Mann, and colleagues from Guy's and St Thomas' Hospital NHS Trust, London, UK, have developed and implemented the first QF PCR trisomy testing service in the UK NHS. They report the data for the first year of the service, in which 1148 amniotic fluid samples, 188 chorionic villus samples, and 37 fetal tissue samples were tested. All samples were also assessed by karyotype analysis. QF-PCR results were obtained and reported on 1314 (98%) of the prenatal samples; the remaining 22 (2%) were uninformative because of maternal-cell contamination. There were no misdiagnoses as confirmed by karyotype analysis. The average reporting time for the last 4 months of data collection was 1.25 working days.

Caroline Ogilvie comments: "Rapid testing of all prenatal samples for autosomal trisomies has been widely welcomed by health professionals and pregnant women. First and foremost, the fast turnaround time means that women with normal results receive prompt reassurance, and abnormalities are identified earlier, leading to better pregnancy management. Our experience indicates that the service itself is low-cost and efficient in terms of labour and consumables, with potential for high-throughput of samples involving minimum extra investment in staff time. Logically, therefore, all prenatal samples from a large region could be tested at a single centre. A nationwide discussion concerning the provision of QF-PCR rapid trisomy testing for all at-risk pregnancies and the identification of appropriate testing centres is now urgently required."

In an accompanying Commentary (p 1030) Matteo Adinolfi from University College London, UK, states: "...Mann and colleagues suggest that QF-PCR should always be followed by conventional cytogenetic tests until such time that there are sufficient data to establish that full karyotype can be reserved for special cases. This view was supported by the majority of people who attended a special meeting of the British Society for Human Genetics in York on Sept 10, 2001, at which votes on this issue were cast. However, since numerical disorders of chromosomes 21, 18, 13, X, and Y are the commonest causes of aneuploidies, with the use of multiplexes with several markers for each chromosome, only a small percentage of affected fetuses may not be diagnosed. Out of every 100 mothers aged over 36 years who are investigated, only about 2-3% are expected to have fetuses with chromosome disorders; of these nearly 98% will have chromosome abnormalities that can be diagnosed by QF-PCR."
Contact: Dr Caroline Ogilvie, c/o Kate Oake, Communications Department, Guy's and St. Thomas' Hospital, Trust, St Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK; T) 44-20-7922-8120; F) 44-20-7633-0347; E)

Professor Matteo Adinolfi, Galton Laboratory and Department of Obstetrics and Gynaecology, University College London, ,London NW1 2HE, UK; F) 44-20-7387-3496; E)


Related Chromosome Articles from Brightsurf:

The bull Y chromosome has evolved to bully its way into gametes
In a new study, published Nov. 18 in the journal Genome Research, scientists in the lab of Whitehead Institute Member David Page present the first ever full, high-resolution sequence of the Y chromosome of a Hereford bull.

Evolution of the Y chromosome in great apes deciphered
New analysis of the DNA sequence of the male-specific Y chromosomes from all living species of the great ape family helps to clarify our understanding of how this enigmatic chromosome evolved.

The male Y chromosome does more than we thought
While the Y chromosome's role was believed to be limited to the functions of the sexual organs, an University of Montreal's scientist has shown that it impacts the functions of other organs as well.

The birth of a male sex chromosome in Atlantic herring
The evolution of sex chromosomes is of crucial importance in biology as it stabilises the mechanism underlying sex determination and usually results in an equal sex ratio.

Why the 'wimpy' Y chromosome hasn't evolved out of existence
The Y chromosome has shrunken drastically over 200 million years of evolution.

Novel insight into chromosome 21 and its effect on Down syndrome
A UCL-led research team has, for the first time, identified specific regions of chromosome 21, which cause memory and decision-making problems in mice with Down syndrome, a finding that provides valuable new insight into the condition in humans.

Breakthrough in sex-chromosome regulation
Researchers at Karolinska Institutet in Sweden have uncovered a chromosome-wide mechanism that keeps the gene expression of sex chromosomes in balance in our cells.

B chromosome first -- mechanisms behind the drive of B chromosomes uncovered
B chromosomes are supernumerary chromosomes, which often are preferentially inherited and showcase an increased transmission rate.

Unveiling disease-causing genetic changes in chromosome 17
Extensive single Watson-Crick base pair mutations can occur in addition to duplication or deletion of an entire group of genes on chromosomal region 17p11.2.

What causes rats without a Y chromosome to become male?
A look at the brains of an endangered spiny rat off the coast of Japan by University of Missouri (MU) Bond Life Sciences Center scientist Cheryl Rosenfeld could illuminate the subtle genetic influences that stimulate a mammal's cells to develop as male versus female in the absence of a Y chromosome.

Read More: Chromosome News and Chromosome Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to