What is qf pcr

Overall, 22 samples have been analysed. The detection rate of aneuploidies of the selected chromosomes 13, 18 and 21, and X and Y was QF-PCR might play a major role and be considered a valid alternative to the full karyotype.

Conversely, following detection of fetal anatomical defects on ultrasound, it is not defined to what extent the risk of aneuploidies unlikely to be diagnosed by QF-PCR is increased. Increased nuchal translucency, for example, is the commonest anatomical marker which can be identified at the first trimester scan.

This is without any doubt a robust method of selecting women at increased risk of chromosomal anomalies, a variety of genetic syndromes and some structural malformations which will become apparent later in gestation Jenderny et al. QF-PCR, therefore, would be a suitable method of analysis for pregnancies with an increased nuchal translucency and conventional cytogenetics would add little in diagnostic accuracy.

Similarly, Comas Gabriel et al. There was only one structural rearrangement, one 22q deletion and two rare trisomies 7 and On the other hand, Paladini et al.

The chromosomal abnormalities which were not trisomy 21, 18, 13 and Turner's syndromes were one in seven 14 out of Howe et al. Therefore, QF-PCR would have failed to detect the majority of aneuploidies in a series of fetuses with diaphragmatic hernia. In cases of increased nuchal translucency, or early cardiac malformations, it could be proposed that in view of the low rate of non-detectable abnormalities with QF-PCR, there is no need to perform a full karyotype, whereas this would not be the case with diaphragmatic hernia or some cardiac defects diagnosed later in gestation.

The main purpose of invasive prenatal diagnosis is to offer prospective parents, who choose to undergo such a procedure, the assurance of having unaffected children when the risk of having a child with a specific genetic disorder chromosomal or monogenic is deemed unacceptably high.

However, it a selective procedure. In other words, it does not allow diagnosis of all congenital defects, but only of a very limited number of these. The issue is how large this number should be within the framework of current techniques. Public health policies in prenatal diagnosis may collide with the need to maintain individual autonomy of decision-making Wenstrom, Clinical practice is dependent on what has been made available by improvements in technology and by its delivery to large segments of the population.

Invasive prenatal diagnosis is nowadays easily accessible, at least in the Western world. Those women who undergo amniocentesis or CVS do so mainly because they perceive or are told that the risk of Down's syndrome is increased above a threshold that is either predefined by the health system or is greater than the one they can accept. In both instances, the risk estimate is based purely on some algorithm which assesses the risk of autosomal aneuploidies and of nothing else.

Since Down's syndrome at birth is by far the commonest of these and the one which most people are aware of, the whole process is tailored to identify, and, eventually, offer termination of fetuses with trisomy Various screening programmes have been implemented in the last decade.

All of them, from asking maternal age through biochemical testing of maternal blood to integrated tests which include ultrasonographic and biochemical markers, are evaluated on the ability to detect the largest number of trisomy 21 fetuses with the lowest percentage of women who are selected to undergo invasive procedures false positive rates.

Yet, once amniocentesis or CVS have been performed, a great deal of information is provided. Fetal sex and heterochromosome anomalies are disclosed, but the impact of these on the health of the child has never been properly assessed, and it might be argued that the benefit of knowing whether the future child has, for example, XYY or XXX is questionable Abramsky and Chapple, ; Christian et al. Structural anomalies may be relevant, but a large number of these are a cause of parental anxiety and they hardly produce a measurable benefit.

In general, these results come unexpectedly, and provide information which is difficult to assess properly and convey. However, the public may be lead to believe that invasive tests give additional information of an unknown extent which may well be greater than what is currently possible , and the opinion is reinforced that all women, irrespective of the risk for which they are selected, have the right to know and missing that information would be a great loss.

It reflects the legacy of how prenatal diagnosis was established: a sophisticated tool for a few high risk patients who were investigated by a complex technique to evaluate the full karyotype, well beyond the initial indication for which the test was done. In recent years two different phenomena have occurred which may well change this attitude. The number of women who undergo invasive prenatal diagnosis has increased throughout the Western world, which is a burden to the health systems in a period of widespread restriction and careful evaluation of how scarce resources are allocated.

In addition, the public has developed exceedingly high, even unrealistic, expectations about the ability of prenatal diagnosis in identifying congenital defects Marteau, In a recent cost-utility analysis, Harris et al.

The desire for reassurance of not having a chromosomally abnormal fetus is the main variable in establishing the cost-effectiveness of prenatal diagnosis, if the decrease in quality of life resulting from not having such information is factored. Although the care providers should have more communication skills than at present, the final decision on whether to undergo prenatal diagnosis or not should be based on both risk estimation and assessment of women's preferences Marteau and Dormandy, ; Petrou and Mugford, This would constitute a complete change of direction compared with the current trend towards objective risk assessment based on a combination of age, biochemical and ultrasonographic variables.

Such an approach has the advantage of selecting women who are at a higher risk of aneuploidies, and mainly trisomy 21, above a preselected threshold, thus allowing better allocation of public resources than one based on individual perception of risk. However, the measures by which these combinations of tests are evaluated false positive and false negative rates are relevant for health providers, but may be meaningless to individual women for whom positive and negative predictive values are eventually more important.

The choice is more likely to be driven by the risk of having positive predictive value or the chances of not having negative predictive value an abnormal fetus, given that specific risk estimation, and the very personal perception of how relevant this estimation is, and how serious is the possible unwanted outcome whether the loss of healthy fetus or the birth of an affected child.

Within this changed panorama in the field of invasive prenatal diagnosis, QF-PCR might play a major role and be considered a valid alternative to the full karyotype. These error rates might be deemed acceptable, although most structural chromosomal anomalies and some sex chromosomes would be missed.

At present, however, women are rarely informed about the full spectrum of the conditions which might be diagnosed via amniocentesis or CVS, besides the most common anomalies. Results of studies of prenatal diagnosis of chromosomal aneuploidies using quantitative fluorescent PCR. Prenat Diagn 11 , 23 — Google Scholar.

Prenat Diagn 17 , — Adinolfi M, Pertl B and Sherlock J Rapid detection of aneuploidies by microsatellite and the quantitative fluorescent polymerase chain reaction. Prenat Diagn 24 , — Association of Clinical Cytogeneticists, UK, pp 9 — Lancet , — Prenat Diagn 22 , — Brackertz M, Kubbies M and Feige A Decreased oxygen supply enhances growth in culture of human mid-trimester amniotic fluid cells.

Hum Genet 64 , — Brambati B and Simoni G Diagnosis of fetal trisomy 21 in first trimester. Lancet 1 , Prenat Diagn 7 , — J Obstet Gynecol 10 , 5 —7. Mol Hum Reprod 7 , — Mol Hum Reprod 8 , — Cuckle H Biochemical screening for Down syndrome. Prenat Diagn 14 , — Prenat Diagn 23 , — Am J Obstet Gynecol , — Ferguson-Smith MA and Yates JRW Maternal age specific rates for chromosome aberrations and factors influencing them: report of a European collaborative study on Prenat Diagn 4 , 5 — N Engl J Med , — Prenat Diagn 16 , — Health Technol Assess 7 , 1 — The inability of STR marker analysis to distinguish subjects who are homozygous or monosomic is a major shortcoming when testing for sex chromosome abnormalities.

Incorporating additional X-chromosome STR markers into the analysis will reduce but not eliminate the likelihood of homozygosity.

To facilitate the detection of monosomy X the Devyser QF PCR kits include X-chromosome counting markers for relative quantification of chromosome X to an autosomal chromosome. All items. Related products 1 Medium.

Devyser Placeholder. Devyser Compact. Detects chromosomal aneuploidies and maternal cell contamination MCC. The development of complete human gametes involves two meiotic divisions.

The first meiotic division is the separation of homologous chromosomes and the second separates sister chromatids. Previous studies suggested that in trisomy 21, more errors occur in meiosis I than in meiosis II In the present study, for trisomy 21, This result was in disagreement with a previous study from Europe Differences in ethnicity and genetics may explain, at least in part, the discrepancies. Trisomy 18 is the second most common trisomy syndrome after trisomy 21 5.

It is also important in pre-natal diagnosis due to being associated with a high risk of fetal loss and stillbirth 46 — The present study indicated that in the context of mid-pregnancy diagnosis, trisomy 18 accounted for The extra chromosome of trisomy 18 cases was usually of maternal origin. Indeed, This is different from other autosomal abnormalities, which more frequently arise in meiosis I. About half of the non-disjunction errors occur in meiosis II of oocytes 49 , The results of the present study were consistent with these results and indicated that the stages of meiotic separation affected in trisomy 18 were The present study included certain cases of trisomy 13 and sex chromosome aneuploidy.

In the two cases in which the parents' blood was provided, the aneuploidies were of paternal origin. Paternal sex chromosome non-disjunction is associated with reduced recombination between X and Y 51 , It has been indicated that G-group and sex chromosomes are more likely to exhibit aneuploidy than other chromosomes Most individual autosomes have a disomic frequency of about 0. QF-PCR is not a perfect technique and the results may be negative even in the presence of fetal abnormalities on ultrasound.

Array comparative genomic hybridization aCGH is able to detect copy number variations with high resolution In cases of fetal abnormalities identified on ultrasound but with negative QF-PCR results, aCGH may indeed detect a gain or deletion in a portion of a chromosome.

In the present study, no cases of negative QF-PCR were encountered due to the strict selection criteria applied to the population pregnancies at high risk of aneuploidy. In addition, QF-PCR cannot fully replace the traditional karyotype analysis, but it may be used to screen for common chromosomal aberrations, including trisomy 21, 18 and 13, and sex chromosome aneuploidy 9 — 13 , The advantage of the technique is that the results may be quickly obtained.

In the presence of normal QF-PCR screening test results but fetal abnormalities on ultrasound, more invasive, time-consuming and costly karyotyping may be performed. QF-PCR confirmed the karyotyping results. In addition, karyotyping also identified three cases of chromosomal translocation, which were not detected by QF-PCR. The frequency of aneuploidies was Of note, the present study had certain limitations. The patients were from a single center and their number was relatively small.

However, as the study population, all females with a high risk of aneuploidies were selected from all consecutive and consenting females encountered during the recruitment period according to the criteria. In addition, due to limited funding, the recruitment period was restricted to 18 months.

Of note, increasing the sample size would increase the likelihood of observing false-negative and false-positive results. A multi-center study may further address this issue. In the present study, only the most common aneuploidies were examined, which is a limitation of QF-PCR itself. Additional studies are required to improve the generalizability of these results. It is important to highlight that only a limited number of chromosomes were tested using QF-PCR in the present study.

Testing for additional chromosomes should be developed, examined for cost-benefits and implemented if required 11 , Assessment of parental origin and meiosis stage of non-disjunction errors by QF-PCR may provide additional genetic information for the diagnosis and management of aneuploidy compared to karyotyping alone.

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Arch Iran Med. Evaluation of 13, cases with consideration of using QF-PCR as a stand-alone test according to referral indications.