The future of prenatal diagnosis: rapid testing or full karyotype? An audit of chromosome abnormalities and pregnancy outcomes for women referred for Down's Syndrome testing

Clinical Utility of the Prenatal BACs-on-Beads™ Assay in Invasive Prenatal Diagnosis

Background: The prenatal BACs-on-Beads™ (PNBoBs™) assay has been applied worldwide for prenatal diagnosis. However, there are neither guidelines nor consensus on choosing patients, sample types, or clinical pathways for using this technique. Moreover, different perspectives have emerged regarding its clinical value. This study aimed to evaluate its clinical utility in the context of clinical practice located in a prenatal diagnostic center in Xiamen, a city in southeast China.

Methods: We tested 2,368 prenatal samples with multiple referral indications using both conventional karyotyping and PNBoBs™. Positive results from PNBoBs™ were verified using current gold-standard approaches.

Results: The overall rates for the detection of pathogenic copy number variation (pCNV) by karyotyping and PNBoBs™ were 1.9% (46/2,368) and 2.0% (48/2,368), respectively. The overall detection rate of karyotyping combined with PNBoBs™ for pCNV was 2.3% (54/2,368). A total of 13 cases of copy number variation (CNV)with a normal karyotype were detected by PNBoBs™. Another case with a normal karyotype that was detected as a CNV of sex chromosomes by PNBoBs™ was validated to be maternal cell contamination by short tandem repeat analysis.

Conclusion: Karyotyping combined with PNBoBs™ can improve both the yield and efficiency of prenatal diagnosis and is appropriate in the second trimester in all patients without fetal ultrasound anomalies who undergo invasive prenatal diagnosis.

A multicenter study of fetal chromosomal abnormalities in Chinese women of advanced maternal age

OBJECTIVE

This study aimed to determine the rates of different fetal chromosomal abnormalities among women of advanced maternal age in China and to discuss the possible misdiagnosis risks of newer molecular techniques, for selection of appropriate prenatal screening and diagnostic technologies.

MATERIALS AND METHODS

Second trimester amniocentesis and fetal karyotype results of 46,258 women were retrospectively reviewed. All women were ≥ 35 years old with singleton pregnancies. The rates of clinically significant chromosomal abnormalities (CSCAs), incidence of chromosomal abnormalities, and correlations with age were determined.

RESULTS

From 2001 to 2010, the proportion of women of advanced maternal age undergoing prenatal diagnosis increased from 20% to 46%. The mean age was 37.4 years (range, 35-46 years). A total of 708 cases of CSCAs, with a rate of 1.53% were found. Trisomy 21 was the most common single chromosome abnormality and accounted for 55.9% of all CSCAs with an incidence of 0.86%. Trisomy 13, trisomy 18, and trisomy 21, the most common chromosome autosomal aneuploidies, accounted for 73.6% of all CSCAs, with a rate of 1.13%. As a group, the most common chromosomal aneuploidies (13/18/21/X/Y) accounted for 93.9% of all abnormalities, with a rate of 1.44%. The incidence of trisomy 21, trisomy 13/18/21 as a group, and 13/18/21/X/Y as a group was significantly greater in women aged 39 years and older (p < 0.001), but was not different between women aged 35 years, 36 years, 37 years, and 38 years.

CONCLUSION

These findings may assist in genetic counseling of advanced maternal age pregnant women, and provide a basis for the selection of prenatal screening and diagnostic technologies.

Couple's Narratives of Communion and Isolation Following Abnormal Prenatal Microarray Testing Results

In 2% to 3% of cases, prenatal microarray testing detects deletions and duplications in a fetus' genome that are undetected by conventional cytogenetics. Many of these changes are associated with variable or uncertain symptomatology. Little is known about how couples experience uncertain results. This study analyzed 24 interviews with members of 12 heterosexual U.S. couples who received pathogenic or uncertain microarray prenatal testing results. Researchers used narrative analysis to examine couples' understanding and incorporation of findings into decision making regarding pregnancy termination. Couples felt unprepared for these findings and frustrated because scant information was available to aid interpretation. Women sought information and made decisions, and men marginalized their distress to support their wives. A shift in voice from first to second person indicated attempts to normalize emotional responses by making the process "common" to all couples. Families pursuing highly sensitive prenatal testing may need expert guidance to support decision making.

Benefits and burdens of using a SNP array in pregnancies at increased risk for the common aneuploidies

We present the nature of pathogenic SNP array findings in pregnancies without ultrasound (US) abnormalities and show the additional diagnostic value of SNP array as compared with rapid aneuploidy detection and karyotyping. 1,330 prenatal samples were investigated with a 0.5-Mb SNP array after the exclusion of the most common aneuploidies. In 2.7% (36/1,330) of the cases, pathogenic chromosome aberrations were found; a microscopically detectable abnormality in 0.7% and a submicroscopic aberration in 2%. Our results show that in addition to the age- or screening-related aneuploidy risk, in pregnancies without US abnormalities, there is a risk of 1:148 (9/1,330) for a (sub)microscopic abnormality associated with an early-onset often severe disease, 1:222 (6/1,330) for a submicroscopic aberration causing an early-onset disease, 1:74 (18/1,330) for carrying a susceptibility locus for a neurodevelopmental disorder, and 1:443 (3/1,330) for a late-onset disorder (hereditary neuropathy with liability to pressure palsies in all three cases). These risk figures are important for adequate pretest counseling so that prospective parents can make informed individualized choices between targeted prenatal testing and broad testing with SNP array. Based on our results, we believe if invasive testing is performed, SNP array should be the preferred cytogenetic technique irrespective of the indication.

Chromosome aberrations identified by cytogenetic analysis of the first two clones of cultured amniotic fluid cells compared with QF-PCR results

We report on our experience of studying amniotic fluid cells by cytogenetic analysis (CA) of the first 2 clones. We investigated the incidence and types of chromosome aberrations detected by CA of 196 amniocenteses performed on pregnant women at high risk. Of these cases, 178 were analysed by QF-PCR (risk group A). The results were compared with the data obtained by CA of 1,263 amniocenteses carried out in patients with other indications. QF-PCR was used to investigate 1,030 of these cases (risk group B). The combined average turnaround time for a CA result of the first 2 clones in both risk groups was within 9 ± 2 days. The final CA results (≥6 clones) were obtained within 12 ± 4 days. In risk group A, CA was not possible in 2 cases due to cell culture failure. The foetal karyotype was abnormal in 13.8% of the cases by CA of ≥6 clones and in 13.5% of the cases by QF-PCR. Together, CA of ≥6 clones and QF-PCR detected chromosome aberrations in 14.8% of the cases. With the exception of 2 cases of in vitro culture failure and 1 case with low gonosomal mosaicism, CA of the first 2 clones detected all cases with chromosome aberrations. Five cases with clinically significant chromosome aberrations were not detected by QF-PCR. In risk group B, the foetal karyotype was found to be abnormal in 2.2% of the cases by CA of ≥6 clones and in 1.0% of the cases by QF-PCR. Together, CA of ≥6 clones and QF-PCR revealed chromosome aberrations in 2.2% of the cases. With the exception of 1 case with low gonosomal mosaicism, CA of the first 2 clones detected all other cases with chromosome aberrations. The majority of these cases were inherited chromosome aberrations. Eighteen cases with chromosome aberrations were not detected by QF-PCR. Based on our results, CA of ≥6 clones, together with QF-PCR as a first test, should be performed in all prenatal cases with abnormal ultrasound findings. In pregnancies with other indications, CA of the first 2 clones alone is sufficient to identify all clinically significant (and inherited) chromosome aberrations.

The impact of national guidance for anomaly screening and invasive testing: unintended consequences

Recent guidance from the UK National Screening Committee (NSC) and the Fetal Anomaly Screening Programme (FASP) has led to important changes in prenatal ultrasound diagnosis and invasive testing. These relate to prenatal ultrasound investigation of what were previously known as 'soft markers' for Down's syndrome at the time of the detailed anomaly scan and as to whether full karyotype or FISH (fluorescent in situ hybridisation)/QFPCR (quantitative fluorescence PCR) testing for trisomies should be carried out when an invasive test is performed. Neither recommendation is directly related to the other but both in combination could have profound implications for the detection of chromosomal abnormalities other than trisomy 21 (Down's syndrome). In the light of two cases recently managed in one regional fetal medicine unit, we retrospectively reviewed cases where, with correct application of the NSC and FASP recommendations, non-lethal and clinically important chromosomal abnormalities would most likely not have been detected.

Slovenian five-year experiences with rapid prenatal diagnosis of common chromosome aneuploidies using quantitative-fluorescence polymerase chain reaction

OBJECTIVE

Quantitative-fluorescence polymerase chain reaction (QF-PCR) was used to detect common fetal aneuploidies in pregnancies with increased (maternal age) or high risk (increased nuchal translucency, abnormal fetal ultrasonography, positive biochemical hormone test, or positive family history) for fetal aneuploidy.

METHODS

The QF-PCR testing was performed on 642 prenatal samples (73.3% amniotic fluids, 26.7% chorionic villus). DNA from prenatal samples were analyzed using an in-house-developed QF-PCR method with 20 micro-satellite markers located on the chromosomes 13, 18, 21, X and Y. Karyotyping of the 392 samples was done and both results were compared.

RESULTS

634/642 samples were successfully analyzed. In 7.1% of 634 cases numerical chromosome abnormalities were detected. Results of QF-PCR and karyotyping were compared in 392 cases. In the group, with increased risk of fetal trisomy the specificity and sensitivity of QF-PCR method was 100%. Among cases with high risk for fetal aneuploidy, sensitivity was 100% (86.6%-100%); however, the specificity was lower, 91.1% to 100%, depending on the referral reason.

CONCLUSIONS

In women, at advanced age QF-PCR can be used alone without karyotyping. In cases with higher risk, especially those with abnormal ultrasound findings, analysis performed only with QF-PCR is not a sufficient diagnostic method.

QF-PCR: application, overview and review of the literature

Quantitative fluorescent polymerase chain reaction has been in diagnostic use in the UK for over 10 years and has proved to be a cost-effective, robust and accurate rapid prenatal test for common aneuploidies. Specific advantages include detection of triploidy, mosaicism and maternal cell contamination. Its application at our centre is described, with developments including stand-alone testing and improvements in strategies for the preparation and testing of chorionic villus biopsies.

Reproductive decisions after fetal genetic counselling

A broad range of testing modalities for fetal genetic disease has been established. These include carrier screening for single-gene mutations, first-trimester and second-trimester screening for chromosome abnormalities and open neural-tube defects, prenatal diagnosis by means of chorionic villus sampling and amniocentesis, and preimplantation genetic diagnosis. Reproductive decisions before and after fetal genetic counselling represent the culmination of a dynamic interaction between prospective parents, obstetrician and genetic counsellor. The decision to undergo genetic testing before and after genetic counselling is influenced by a host of interrelated factors, including patient-partner and family relationships, patient-physician communication, societal mores, religious beliefs, and the media. Because of the complexity of personal and societal factors involved, it is not surprising that genetic counselling concerning reproductive decision-making must be individualised. A limited number of principles, guidelines and standards apply when counselling about testing for fetal genetic disease. These principles are that genetic counselling should be non-directive and unbiased and that parental decisions should be supported regardless of the reproductive choice. A critical responsibility of the obstetrician and genetic counsellor is to provide accurate and objective information about the implications, advantages, disadvantages and consequences of any genetic testing applied to prospective parents and their fetuses. These principles and responsibilities will be tested as newer technologies, such as array comparative genome hybridisation, non-invasive prenatal diagnosis and sequencing of the entire genome are introduced into the field of reproductive genetics and become routine practice.

Dual testing with QF-PCR and karyotype analysis for prenatal diagnosis of chromosomal abnormalities. Evaluation of 13,500 cases with consideration of using QF-PCR as a stand-alone test according to referral indications

OBJECTIVE

Evaluate the results obtained from Quantitative Fluorescent (QF)-PCR and conventional karyotype analysis to determine the advantages and disadvantages of dual testing in prenatal diagnosis.

METHODS

From 1 June 2006 to 1 June 2010, dual testing by QF-PCR and karyotype analysis was performed in 13,500 prenatal samples. The rates of concordant results between the two methods were evaluated and the rates of clinically significant chromosomal abnormalities undetected by QF-PCR were assessed.

RESULTS

Abnormal karyotype was found in 320 out of 13,500 cases (2.37%, 95% confidence interval (CI) 2.11-2.63%). From these, QF-PCR did not detect the abnormality in 70 cases (0.52%, 95% CI 0.4-0.64%), whereas 34 had a high/unknown risk of adverse outcome (0.25%, 95% CI 0.17-0.33%). By selectively applying dual testing only at cases with ultrasound findings and/or genetic history, 13 cases of high/unknown risk would have been missed (0.1%, 95% CI 0.05-0.15%).

CONCLUSION

Selective dual testing is expected to achieve a serious beneficial economical outcome and reduce parental anxiety produced by ambiguous cytogenetic findings. However, the percentage of 0.1% undetected clinically significant abnormalities cannot be ignored. A suggestion would include the offering of a choice to the pregnant women, undergoing prenatal screening, by informing them about different approaches and various complications.

Is routine karyotyping required in prenatal samples with a molecular or metabolic referral?

As a routine, karyotyping of invasive prenatal samples is performed as an adjunct to referrals for DNA mutation detection and metabolic testing. We performed a retrospective study on 500 samples to assess the diagnostic value of this procedure. These samples included 454 (90.8%) chorionic villus (CV) and 46 (9.2%) amniocenteses specimens. For CV samples karyotyping was based on analyses of both short-term culture (STC) and long-term culture (LTC) cells. Overall, 19 (3.8%) abnormal karyotypes were denoted: four with a common aneuploidy (trisomy 21, 18 and 13), two with a sex chromosomal aneuploidy (Klinefelter syndrome), one with a sex chromosome mosaicism and twelve with various autosome mosaicisms. In four cases a second invasive test was performed because of an abnormal finding in the STC. Taken together, we conclude that STC and LTC karyotyping has resulted in a diagnostic yield of 19 (3.8%) abnormal cases, including 12 cases (2.4%) with an uncertain significance. From a diagnostic point of view, it is desirable to limit uncertain test results as secondary test findings. Therefore, we recommend a more targeted assay, such as e.g. QF-PCR, as a replacement of the STC and to provide parents the autonomy to choose between karyotyping and QF-PCR.

Rapid aneuploidy detection or karyotyping? Ethical reflection

No consensus exists whether women at increased risk for trisomy 21, 13, and 18 should be offered stand-alone rapid aneuploidy detection (RAD) or karyotyping. In this paper, the ethical implications of a fast, relatively cheap and targeted RAD are examined. The advantages of RAD seem less robust than its proponents suggest. Fast test results only give a short-term psychological benefit. The cost advantage of RAD is apparent, but must be weighed against consequences like missed abnormalities, which are evaluated differently by professionals and pregnant women. Since pre-test information about RAD will have to include telling women about karyotyping as a possible alternative, the advantage of RAD in terms of the quantity of information that needs to be given may also be smaller than suggested. We conclude that none of the supposed arguments in favour of RAD is decisive in itself. Whether the case for RAD may still be regarded as convincing when taking these arguments together seems to depend on one's implicit view of what prenatal screening is about. Are we basically dealing with a test for trisomy 21 and a few conditions more? Or are there good grounds for also testing for the wider range of abnormalities that karyotyping can detect? As professionals and pregnant women may have different views about this, we suggest that the best approach is to offer women a choice between RAD and karyotyping. This approach is most in line with the general aim of prenatal screening: providing opportunities for autonomous reproductive choice.

Economic evaluation of multiplex ligation-dependent probe amplification and karyotyping in prenatal diagnosis: a cost-minimization analysis

Purpose

To assess the cost-effectiveness of Multiplex Ligation-dependent Probe Amplification (MLPA, P095 kit) compared to karyotyping.

Methods

A cost-minimization analysis alongside a nationwide prospective clinical study of 4,585 women undergoing amniocentesis on behalf of their age (≥36 years), an increased risk following first trimester prenatal screening or parental anxiety.

Results

Diagnostic accuracy of MLPA (P095 kit) was comparable to karyotyping (1.0 95% CI 0.999–1.0). Health-related quality of life did not differ between the strategies (summary physical health: mean difference 0.31, p = 0.82; summary mental health: mean difference 1.91, p = 0.22). Short-term costs were lower for MLPA: mean difference €315.68 (bootstrap 95% CI €315.63–315.74; −44.4%). The long-term costs were slightly higher for MLPA: mean difference €76.42 (bootstrap 95% CI €71.32–81.52; +8.6%). Total costs were on average €240.13 (bootstrap 95% CI €235.02–245.23; −14.9%) lower in favor of MLPA. Cost differences were sensitive to proportion of terminated pregnancies, sample throughput, individual choice and performance of tests in one laboratory, but not to failure rate or the exclusion of polluted samples.

Conclusion

From an economic perspective, MLPA is the preferred prenatal diagnostic strategy in women who undergo amniocentesis on behalf of their age, following prenatal screening or parental anxiety.

Electronic supplementary material

The online version of this article (doi:10.1007/s00404-011-1921-y) contains supplementary material, which is available to authorized users.

Rapid screening for chromosomal aneuploidies using array-MLPA

Background

Chromosome abnormalities, especially trisomy of chromosome 21, 13, or 18 as well as sex chromosome aneuploidy, are a well-established cause of pregnancy loss. Cultured cell karyotype analysis and FISH have been considered reliable detectors of fetal abnormality. However, results are usually not available for 3-4 days or more. Multiplex ligation-dependent probe amplification (MLPA) has emerged as an alternative rapid technique for detection of chromosome aneuploidies. However, conventional MLPA does not allow for relative quantification of more than 50 different target sequences in one reaction and does not detect mosaic trisomy. A multiplexed MLPA with more sensitive detection would be useful for fetal genetic screening.

Methods

We developed a method of array-based MLPA to rapidly screen for common aneuploidies. We designed 116 universal tag-probes covering chromosomes 13, 18, 21, X, and Y, and 8 control autosomal genes. We performed MLPA and hybridized the products on a 4-well flow-through microarray system. We determined chromosome copy numbers by analyzing the relative signals of the chromosome-specific probes.

Results

In a blind study of 161 peripheral blood and 12 amniotic fluid samples previously karyotyped, 169 of 173 (97.7%) including all the amniotic fluid samples were correctly identified by array-MLPA. Furthermore, we detected two chromosome X monosomy mosaic cases in which the mosaism rates estimated by array-MLPA were basically consistent with the results from karyotyping. Additionally, we identified five Y chromosome abnormalities in which G-banding could not distinguish their origins for four of the five cases.

Conclusions

Our study demonstrates the successful application and strong potential of array-MLPA in clinical diagnosis and prenatal testing for rapid and sensitive chromosomal aneuploidy screening. Furthermore, we have developed a simple and rapid procedure for screening copy numbers on chromosomes 13, 18, 21, X, and Y using array-MLPA.

Rapid methods for targeted prenatal diagnosis of common chromosome aneuploidies

Improvements in non-invasive screening methods for trisomy 21 (Down syndrome) and other aneuploidies during the first and second trimester of pregnancy have radically changed the indications for prenatal diagnosis over the last decade. Consequently, there was a need for rapid tests for the detection of common chromosome aneuploidies resulting in the development of molecular methods for the rapid, targeted detection of (an)euploidies of the chromosomes 13, 18, 21 and the sex chromosomes. The analysis of large series of prenatal samples has shown that such tests can detect the great majority of chromosome abnormalities in prenatal diagnosis. This resulted in lively discussions on whether conventional karyotyping should remain the standard method for the majority of prenatal cases or can be replaced by rapid tests only. This review gives an overview of different aspects of the three most common tests for rapid, targeted prenatal detection of (an)euploidies, i.e. interphase fluorescence in-situ hybridisation (iFISH), quantitative fluorescent polymerase chain reaction (QF-PCR) and multiplex ligation-dependent probe amplification (MLPA).

Individualized choice in prenatal diagnosis: the impact of karyotyping and standalone rapid aneuploidy detection on quality of life

OBJECTIVE

To assess the reasons and perceptions of women who are offered a choice between karyotyping and standalone rapid aneuploidy detection (RAD) and to compare the impact of both tests on anxiety and health-related quality of life.

METHODS

In this prospective comparative study, women undergoing amniocentesis on behalf of their age or for an increased Down syndrome risk were offered a choice between karyotyping (group 1, n = 68) and standalone RAD (group 2, n = 61). Follow-up was 9 weeks post amniocentesis.

RESULTS

The most commonly cited reason for choosing karyotyping was obtaining as much information as possible, while for choosing standalone RAD, it was the short waiting time. Prenatal screening (OR 7.09), no knowledge of karyotyping (OR 4.2), and an intermediate perceived risk for chromosomal abnormalities (OR 3.6) were associated with choosing standalone RAD. There were no systematic differences in time of karyotyping and standalone RAD in terms of anxiety (P = 0.11), generic physical and mental health (P = 0.94, 0.52; P = 0.66, 0.07), personal perceived control (PPC; P = 0.69), and stress (P = 0.66).

CONCLUSION

Offering a choice between karyotyping and standalone RAD does not influence anxiety, stress, PPC, or generic health. Individual choice in prenatal diagnosis meets individual needs and thereby could reduce anxiety and stress.

Rapid and novel prenatal molecular assay for detecting aneuploidies and microdeletion syndromes

OBJECTIVES

To develop a targeted aneuploidy and microdeletion detection platform for use in the prenatal setting, to assess the integrity of the platform with a robust validation system, and to prospectively determine the performance of the platform under routine clinical conditions.

METHODS

To generate proxies for the various disorders assessed by the assay for analytical validation purposes, cells from ten microdeletion syndromes as well as from common aneuploidies were spiked into cleared amniotic fluid. Genomic DNA was isolated, labeled, and hybridized to microbeads that have been coupled to DNA derived from Bacterial Artificial Chromosome (BAC) from the relevant regions targeted by the array. Beads were read using a flow cytometric multiplex bead array detection system. In the prospective part of the study, 104 amniotic fluid samples were collected and analyzed.

RESULTS

All microdeletion syndromes and aneuploidies were validated in a blinded fashion. In the prospective study, the total number of readable samples was 101 of 104 (97%). All sample results were confirmed independently.

CONCLUSION

The bead array approach is a rapid and reliable test for detecting aneuploidies and microdeletions. This assay has the potential to provide the benefit of expanded molecular cytogenetic testing to pregnant women undergoing invasive prenatal diagnosis. This approach may be especially useful in parts of the world where cytogenetic personnel and facilities may be limited.

Rapid aneuploidy testing versus traditional karyotyping in amniocentesis for certain referral indications

OBJECTIVE

(1) To determine the suitability of replacing full karyotype analysis with quantitative fluorescent polymerase chain reaction (QF-PCR) for prenatal diagnosis in amniotic fluid samples obtained by amniocentesis. (2) To evaluate an indication-based classification of cases at risk of missing clinically relevant chromosomal disorders by QF-PCR.

METHODS

We reviewed all fetal karyotypes obtained by amniocentesis between January 2004 and December 2008. We compared the cytogenetic findings obtained through conventional karyotype with those that would have been theoretically obtained using QF-PCR.

RESULTS

Of the 4007 karyotypes obtained, 110 abnormal karyotypes were found (2.8%). Out of these, 30 (27%) were chromosomal abnormalities (CA) which would not have been detected by PCR alone. These included 16 cases (53%) predicted to confer no increased risk, 9 (30%) predicted to have a low risk, and 5 (17%) with an uncertain or high risk of fetal abnormality. A policy of QF-PCR alone would have identified 80 of 85 (94%) clinically significant CA. When QF-PCR shows a normal result, the overall residual risk is 0.75% for any CA and 0.12% for a clinical significant CA.

CONCLUSION

In our population, a policy of QF-PCR alone would miss 0.12% clinically relevant CA. QF-PCR directed to common aneuploidies can be considered as an economically and clinically acceptable prenatal diagnosis policy, offering full karyotype only for specific indications.

Different communication strategies for disclosing results of diagnostic prenatal testing

BACKGROUND

Any screening program aiming to reassure pregnant women that their unborn baby is healthy will cause anxiety while waiting for the test results.

OBJECTIVES

1) To determine if revealing amniocentesis or chorionic villous sampling (CVS) results on a fixed date alters maternal anxiety during the waiting period, compared with a policy of revealing the result "when available" (i.e. variable date). 2) To evaluate whether issuing early results from a rapid molecular test alters maternal anxiety during the waiting period. 3) To evaluate whether different methods of communication (telephone, fax, email, face to face) have any impact on the parents' satisfaction and anxiety levels.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2010).

SELECTION CRITERIA

All published and unpublished randomised trials, in which methods of issuing prenatal test results are compared.

DATA COLLECTION AND ANALYSIS

Two review authors (Faris Mujezinovic and Zarko Alfirevic) assessed eligibility and trial quality and performed data extraction.

MAIN RESULTS

Two studies (involving 286 women) from amniocentesis (but none from CVS) compared the impact of communicating results of rapid testing with waiting for definitive karyotype. Unfortunately, it was not possible to perform pooled analysis because one study reported only median (interquartile range) data, presumably because the data were not normally distributed.One study reported a statistically significant reduction in the average anxiety during the waiting period for women who had had a rapid test compared with those who had not (mean difference (MD) -2.30, 95% confidence intervals (CI) -3.08 to - 1.52). The other study compared median (interquartile range) for the trait- and state-anxiety scores and found no difference between the two groups.

AUTHORS' CONCLUSIONS

We found no conclusive evidence that, while waiting for the full karyotype following amniocentesis, issuing results from a rapid analysis reduces maternal anxiety. The limited evidence from the two trials included in this review does not help resolve the dilemma about whether full karyotyping should be abandoned in favour of limited rapid testing for women undergoing Down's syndrome screening. This choice will rest on clinical arguments and cost-effectiveness rather than impact on anxiety.There is also no evidence to support the view that issuing amniocentesis results as soon as they are available is more user friendly than using a pre-defined fixed date. Studies evaluating the effect of different strategies for disclosing results on women anxiety for CVS are needed.

Assessment of QF-PCR as the first approach in prenatal diagnosis

Quantitative fluorescent PCR (QF-PCR) has been used by many laboratories for prenatal diagnosis of the most common aneuploidies. QF-PCR is rapid, cost-effective, and suitable for automation and can detect most abnormalities diagnosed by conventional karyotyping. Whether QF-PCR should be used alone in most of the samples and in which karyotyping should also be offered is currently a topic of debate. We evaluated and compared the results obtained from 7679 prenatal samples in which conventional karyotype and QF-PCR had been performed, including 1243 chorionic villi and 6436 amniotic fluid samples. Concordant QF-PCR and karyotype results were obtained in 98.75% of the samples. An abnormal karyotype associated with adverse clinical outcome undetected by QF-PCR was found in 0.05% of samples. Therefore, QF-PCR can be used alone in a large number of samples studied in a prenatal laboratory, thereby reducing both the workload in cytogenetic laboratories and parental anxiety when awaiting results.

QF-PCR as a stand-alone test for prenatal samples: the first 2 years' experience in the London region

OBJECTIVE

To analyse the results of the first 2 years of a QF-PCR stand-alone testing strategy for the prenatal diagnosis of aneuploidy in the London region and to determine the advantages and disadvantages of this policy.

METHODS

A review of the results of 9737 prenatal samples received for exclusion of chromosome abnormalities. All samples were subjected to QF-PCR testing for common aneuploidies but only samples fulfilling specific criteria subsequently had a full karyotype analysis.

RESULTS

Of the 9737 samples received, 10.3% had a chromosome abnormality detected by QF-PCR testing. Of the 7284 samples received with no indication for karyotype analysis, 25 (0.3%) received a normal QF-PCR result but subsequently had an abnormal karyotype detected either prenatally as a privately funded test or postnatally. Of these samples, without subsequent abnormal ultrasound findings, five had a chromosome abnormality associated with a poor prognosis, representing 0.069% of samples referred for Down syndrome testing.

CONCLUSION

While back-up karyotyping is required for some samples, using QF-PCR as a stand-alone prenatal test for pregnancies without ultrasound abnormalities reduces costs, provides rapid delivery of results, and avoids ambiguous and uncertain karyotype results, reducing parental anxiety.

The impact of rapid aneuploidy detection (RAD) in addition to karyotyping versus karyotyping on maternal quality of life

OBJECTIVE

To assess the impact of rapid aneuploidy detection (RAD) combined with fetal karyotyping versus karyotyping only on maternal anxiety and health-related quality of life.

METHODS

Women choosing to undergo amniocentesis were selected into group 1, i.e. receiving a karyotype result only (n = 132) or to group 2, i.e. receiving both the result of RAD and karyotyping (n = 181).

RESULTS

There were no systematic differences in time of RAD combined with karyotyping versus karyotyping only in terms of anxiety (P = 0.91), generic physical health (P = 0.76, P = 0.46), generic mental health (P = 0.52, P = 0.72), personal perceived control (P = 0.91) and stress (P = 0.13). RAD combined with karyotyping reduced anxiety and stress two weeks earlier compared to karyotyping only.

CONCLUSION

RAD as add-on to karyotyping reduces anxiety and stress in the short term but it does not influence overall anxiety, stress, personal perceived control, and generic mental and physical health when compared to a karyotype-only strategy.

Rapid prenatal diagnosis of common chromosome aneuploidies by QF-PCR, results of 9 years of clinical experience

BACKGROUND

Despite being deliberately targeted to common chromosome aneuploidies, the rapid quantitative fluorescent polymerase chain reaction (QF-PCR) tests can detect the majority of chromosome abnormalities in prenatal diagnosis. The main advantages of this assay are low cost, speed and automation allowing large-scale application.

METHODS

We developed a QF-PCR test that was applied on 43 000 clinical samples reporting results in 24 h. Most common indications were biochemical risk (32%) and advanced maternal age (30%). Samples were also tested by cytogenetic analysis and the results compared.

RESULTS

Aneuploidies involving chromosomes 21, 18, 13, X and Y were detected with 100% specificity. Several cases of partial trisomies and mosaicism were also identified. Overall 95% of clinically relevant abnormalities were readily detected and termination of affected pregnancies could be performed without waiting for the cytogenetic results.

CONCLUSIONS

Our study supports the possibility of reducing the load of prenatal cytogenetic tests if the pregnancies are carefully monitored by non-invasive screening. In case of abnormal QF-PCR results, medical action can be taken within few hours from sampling. In cases of negative QF-PCR results, cytogenetic analyses might only be performed for fetuses with ultrasound abnormalities. In countries where large-scale cytogenetic tests are not available, QF-PCR may be used as the only prenatal diagnostic procedure.

PRENATAL SCREENING AND DIAGNOSIS OF FETAL CHROMOSOMAL ABNORMALITIES – DILEMMA BETWEEN BEST EVIDENCE-BASED MODEL AND PRACTICABILITY

There is little doubt that congenital abnormalities cause significant stresses to the affected children, their parents and the whole family. Such stresses can be physical, psychological, social and financial. To society, the cost of looking after these affected individuals properly can be substantial. In the absence of prenatal screening, birth defects affect approximately 2–4% of newborns, although there are significant variations between populations.

Rapid aneuploidy detection with multiplex ligation-dependent probe amplification: a prospective study of 4000 amniotic fluid samples

The introduction of prenatal screening requires rapid high-throughput diagnosis of common aneuploidies. Multiplex ligation-dependent probe amplification (MLPA) allows for quick, easily automated multiplex testing of these aneuploidies in one polymerase chain reaction. We performed a large prospective study using MLPA on 4000 amniotic fluid (AF) samples including all indications and compared its value to karyotyping and fluorescence in situ hybridization (FISH). MLPA can reliably determine common aneuploidies with 100% sensitivity and 100% specificity. Moreover, some mosaic cases and structural chromosome aberrations were detected as well. In cases of a male fetus, triploidies can be detected by an aberrant pattern of probe signals, which mimics maternal cell contamination (MCC). Macroscopic blood contamination was encountered in 3.2% of the AF samples. In 20% of these samples, an MLPA pattern was found consistent with MCC, although there were no false negatives of the most common aneuploidies. As the vast majority of inconclusive results (1.7%) is due to potential MCC, we designed a protocol in which we determine whether MLPA can be performed on blood-contaminated AF samples by testing if blood is of fetal origin. Then, the number of inconclusive results could be theoretically reduced to 0.05%. We propose an alternative interpretation of relative probe signals for rapid aneuploidy diagnosis (RAD). We discuss the value of MLPA for the detection of (submicroscopic) structural chromosome anomalies. MLPA is a reliable method that can replace FISH and could be used as a stand-alone test for RAD instead of karyotyping.

Complete discrepancy between QF-PCR analysis of uncultured villi and karyotyping of cultured cells in the prenatal diagnosis of trisomy 21 in three CVS

OBJECTIVE

To investigate complete discrepancies in the prenatal diagnosis of trisomy 21 between QF-PCR analysis of uncultured villi and karyotyping of cultured cells in three chorion villus samples.

METHODS

Clinical details were obtained from all three patients. Follow-up studies were undertaken where possible by evaluation of chromosome 21 copy number with QF-PCR, interphase FISH, MLPA and karyotyping, and by post-mortem examination.

RESULTS

Case 1: severe oligohydramnios and microcephaly on scan. QF-PCR: trisomy 21; MLPA: trisomy 21; cultured karyotype: 46,XY[48]. Placental and fetal tissue results and post-mortem examination indicated a euploid fetus with trisomy 21 mosaicism confined to the placenta. Case 2: Down screen risk 1:16; NT = 4.4 mm; absent nasal bone (Caucasian mother). QF-PCR: disomy 21; cultured karyotype: 47,XY,+ 21[23]. Neck thickening noted at delivery-post-mortem refused, no fetal tissue available. Placental tissue indicated mosaicism for trisomy 21. Case 3: Down screen risk 1:91; NT = 6.7 mm. QF-PCR: disomy 21; cultured karyotype: 46,XX,der(21;21)(q10;q10)[60]. No follow-up possible. PCR genotyping of cultured cells confirmed sample identity in all three cases. Chromosome 21 markers observed by PCR were biallelic in all three cases, indicating that a mitotic error could account for the presence of the abnormal cell lines in each case.

CONCLUSION

QF-PCR analysis of uncultured villi and cultured karyotyping may rarely show complete discrepancy in the prediction of fetal trisomy 21 in CVS. Within-biopsy sample mosaicism, together with the testing of different cell populations, provide an explanation for these results. Practical ways to minimise the risk of such discrepancy are proposed.

Molecular cytogenetic and rapid aneuploidy detection methods in prenatal diagnosis

Cytogenetic analysis is an important component of prenatal diagnosis. The ability to rapidly detect aneuploidy and identify small structural abnormalities of fetal chromosomes has been greatly enhanced by the use of molecular cytogenetic technologies. In this review, we will present some of the molecular cytogenetic techniques available to the clinical cytogenetics laboratory. These include fluorescence in situ hybridization (FISH), quantitative fluorescence PCR (QF-PCR), multiplex ligation-dependent probe amplification (MLPA) and microarray-based comparative genomic hybridization (array CGH). The benefits and limitations of each technology will be discussed in the context of prenatal diagnosis.

Full karyotyping, rapid aneuploidy diagnosis or both when invasive prenatal testing is performed for diagnosis of thalassaemia?

A retrospective study was performed to compare the detection rate of chromosomal abnormalities by different approaches of full karyotyping, rapid aneuploidy diagnosis (RAD) or both when invasive prenatal testing is performed for diagnosis of thalassaemia. The karyotype results of 1120 prenatal samples obtained from thalassaemia couples from January 1985 to December 2002 in a referral centre for prenatal diagnosis were studied. The detection rate of chromosomal abnormalities by four different approaches were compared: (i) karyotyping for all samples; (ii) RAD (21,18,13,X,Y) for all samples; (iii) RAD for all samples + karyotyping for cases with ultrasound abnormalities; and (iv) RAD (21,18,13) for all + RAD (X,Y) for cases with ultrasound abnormalities consistent with Turner syndrome + karyotyping for cases with ultrasound abnormalities. Normal karyotypes were found in 1103 samples (98.5%). There were 17 cases (1.5%) of chromosomal abnormalities: four cases (0.36%) were clinically significant, eight cases (0.7%) were of borderline clinical significance and five cases (0.44%) were not confirmed by subsequent prenatal or postnatal tests. The incidences of autosomal (7/1120 = 0.63%) and sex chromosomal (5/1120 = 0.45%) abnormalities were not higher than those (0.41 and 0.22%, respectively) from newborn surveys (Hook and Hamerton, 1977) (P = 0.398 and 0.216, respectively). Approach 1 would detect all 17 chromosomal abnormalities. Approach 2 would detect three of four clinically significant chromosomal abnormalities but not detect six of eight chromosomal abnormalities of borderline clinical significance and three of five chromosomal abnormalities not confirmed by subsequent prenatal or postnatal tests. Approach 3, in addition, would be able to detect all four clinically significant chromosomal abnormalities. Approach 4 would detect all four clinically significant chromosomal abnormalities but would not detect seven of eight chromosomal abnormalities of borderline clinical significance and four of five chromosomal abnormalities not confirmed by subsequent prenatal or postnatal tests. RAD (21,18,13) for all + RAD (X,Y) for cases with ultrasound abnormalities consistent with Turner syndrome + karyotyping for cases with ultrasound abnormalities seemed to be the best approach for the detection of chromosomal abnormalities when invasive prenatal testing is performed for diagnosis of thalassaemia.