The value of screening for Down's syndrome in a socioeconomically deprived area with a high ethnic population

First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first trimester ultrasound markers alone, and in combination with first trimester serum tests for the detection of Down's syndrome.

SEARCH METHODS

We carried out extensive literature searches including MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), and The Database of Abstracts of Reviews of Effects (the Cochrane Library 2011, Issue 7). We checked reference lists and published review articles for additional potentially relevant studies.

SELECTION CRITERIA

Studies evaluating tests of first trimester ultrasound screening, alone or in combination with first trimester serum tests (up to 14 weeks' gestation) for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 126 studies (152 publications) involving 1,604,040 fetuses (including 8454 Down's syndrome cases). Studies were generally good quality, although differential verification was common with invasive testing of only high-risk pregnancies. Sixty test combinations were evaluated formed from combinations of 11 different ultrasound markers (nuchal translucency (NT), nasal bone, ductus venosus Doppler, maxillary bone length, fetal heart rate, aberrant right subclavian artery, frontomaxillary facial angle, presence of mitral gap, tricuspid regurgitation, tricuspid blood flow and iliac angle 90 degrees); 12 serum tests (inhibin A, alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (ßhCG), total hCG, pregnancy-associated plasma protein A (PAPP-A), unconjugated oestriol (uE3), disintegrin and metalloprotease 12 (ADAM 12), placental growth factor (PlGF), placental growth hormone (PGH), invasive trophoblast antigen (ITA) (synonymous with hyperglycosylated hCG), growth hormone binding protein (GHBP) and placental protein 13 (PP13)); and maternal age. The most frequently evaluated serum markers in combination with ultrasound markers were PAPP-A and free ßhCG.Comparisons of the 10 most frequently evaluated test strategies showed that a combined NT, PAPP-A, free ßhCG and maternal age test strategy significantly outperformed ultrasound markers alone (with or without maternal age) except nasal bone, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). In both direct and indirect comparisons, the combined NT, PAPP-A, free ßhCG and maternal age test strategy showed superior diagnostic accuracy to an NT and maternal age test strategy (P < 0.0001). Based on the indirect comparison of all available studies for the two tests, the sensitivity (95% confidence interval) estimated at a 5% FPR for the combined NT, PAPP-A, free ßhCG and maternal age test strategy (69 studies; 1,173,853 fetuses including 6010 with Down's syndrome) was 87% (86 to 89) and for the NT and maternal age test strategy (50 studies; 530,874 fetuses including 2701 Down's syndrome pregnancies) was 71% (66 to 75). Combinations of NT with other ultrasound markers, PAPP-A and free ßhCG were evaluated in one or two studies and showed sensitivities of more than 90% and specificities of more than 95%.High-risk populations (defined before screening was done, mainly due to advanced maternal age of 35 years or more, or previous pregnancies affected with Down's syndrome) showed lower detection rates compared to routine screening populations at a 5% FPR. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under-ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting test sensitivity. Conversely, for the NT, PAPP-A, free ßhCG and maternal age test strategy, detection rates and false positive rates increased with maternal age in the five studies that provided data separately for the subset of women aged 35 years or more.

AUTHORS' CONCLUSIONS

Test strategies that combine ultrasound markers with serum markers, especially PAPP-A and free ßhCG, and maternal age were significantly better than those involving only ultrasound markers (with or without maternal age) except nasal bone. They detect about nine out of 10 Down's affected pregnancies for a fixed 5% FPR. Although the absence of nasal bone appeared to have a high diagnostic accuracy, only five out of 10 affected Down's pregnancies were detected at a 1% FPR.

First and second trimester serum tests with and without first trimester ultrasound tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 (or the specific area of chromosome 21 implicated in causing Down's syndrome) rather than two. It is the commonest congenital cause of mental disability. Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal) and false negative screening tests (i.e. a fetus with Down's syndrome will be missed). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester serum markers with and without first trimester ultrasound markers for the detection of Down's syndrome in the antenatal period, as combinations of markers.

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), the Database of Abstracts of Reviews of Effectiveness (the Cochrane Library 25 August 2011), MEDION (25 August 2011), the Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), the National Research Register (Archived 2007), and Health Services Research Projects in Progress database (25 August 2011). We did not apply a diagnostic test search filter. We did forward citation searching in ISI citation indices, Google Scholar and PubMed 'related articles'. We also searched reference lists of retrieved articles SELECTION CRITERIA: Studies evaluating tests of combining first and second trimester maternal serum markers in women up to 24 weeks of gestation for Down's syndrome, with or without first trimester ultrasound markers, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Twenty-two studies (reported in 25 publications) involving 228,615 pregnancies (including 1067 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high risk pregnancies. Ten studies made direct comparisons between tests. Thirty-two different test combinations were evaluated formed from combinations of eight different tests and maternal age; first trimester nuchal translucency (NT) and the serum markers AFP, uE3, total hCG, free βhCG, Inhibin A, PAPP-A and ADAM 12. We looked at tests combining first and second trimester markers with or without ultrasound as complete tests, and we also examined stepwise and contingent strategies.Meta-analysis of the six most frequently evaluated test combinations showed that a test strategy involving maternal age and a combination of first trimester NT and PAPP-A, and second trimester total hCG, uE3, AFP and Inhibin A significantly outperformed other test combinations that involved only one serum marker or NT in the first trimester, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate. However, the evidence was limited in terms of the number of studies evaluating this strategy, and we therefore cannot recommend one single screening strategy.

AUTHORS' CONCLUSIONS

Tests involving first trimester ultrasound with first and second trimester serum markers in combination with maternal age are significantly better than those without ultrasound, or those evaluating first trimester ultrasound in combination with second trimester serum markers, without first trimester serum markers. We cannot make recommendations about a specific strategy on the basis of the small number of studies available.

Urine tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21, or the specific area of chromosome 21 implicated in causing Down's syndrome, rather than two. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life. The risk of a Down's syndrome affected pregnancy increases with advancing maternal age.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester urine markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), EMBASE (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2011, Issue 7), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (archived 2007), Health Services Research Projects in Progress database (25 August 2011). We studied reference lists and published review articles.

SELECTION CRITERIA

Studies evaluating tests of maternal urine in women up to 24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC (receiver operating characteristic) meta-analytical methods to analyse test performance and compare test accuracy. We performed analysis of studies allowing direct comparison between tests. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 19 studies involving 18,013 pregnancies (including 527 with Down's syndrome). Studies were generally of high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Twenty-four test combinations were evaluated formed from combinations of the following seven different markers with and without maternal age: AFP (alpha-fetoprotein), ITA (invasive trophoblast antigen), ß-core fragment, free ßhCG (beta human chorionic gonadotrophin), total hCG, oestriol, gonadotropin peptide and various marker ratios. The strategies evaluated included three double tests and seven single tests in combination with maternal age, and one triple test, two double tests and 11 single tests without maternal age. Twelve of the 19 studies only evaluated the performance of a single test strategy while the remaining seven evaluated at least two test strategies. Two marker combinations were evaluated in more than four studies; second trimester ß-core fragment (six studies), and second trimester ß-core fragment with maternal age (five studies).In direct test comparisons, for a 5% false positive rate (FPR), the diagnostic accuracy of the double marker second trimester ß-core fragment and oestriol with maternal age test combination was significantly better (ratio of diagnostic odds ratio (RDOR): 2.2 (95% confidence interval (CI) 1.1 to 4.5), P = 0.02) (summary sensitivity of 73% (CI 57 to 85) at a cut-point of 5% FPR) than that of the single marker test strategy of second trimester ß-core fragment and maternal age (summary sensitivity of 56% (CI 45 to 66) at a cut-point of 5% FPR), but was not significantly better (RDOR: 1.5 (0.8 to 2.8), P = 0.21) than that of the second trimester ß-core fragment to oestriol ratio and maternal age test strategy (summary sensitivity of 71% (CI 51 to 86) at a cut-point of 5% FPR).

AUTHORS' CONCLUSIONS

Tests involving second trimester ß-core fragment and oestriol with maternal age are significantly more sensitive than the single marker second trimester ß-core fragment and maternal age, however, there were few studies. There is a paucity of evidence available to support the use of urine testing for Down's syndrome screening in clinical practice where alternatives are available.

First trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. However, no test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

The aim of this review was to estimate and compare the accuracy of first trimester serum markers for the detection of Down's syndrome in the antenatal period, both as individual markers and as combinations of markers. Accuracy is described by the proportion of fetuses with Down's syndrome detected by screening before birth (sensitivity or detection rate) and the proportion of women with a low risk (normal) screening test result who subsequently had a baby unaffected by Down's syndrome (specificity).

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 25 August 2011), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (Archived 2007), Health Services Research Projects in Progress database (25 August 2011). We did forward citation searching ISI citation indices, Google Scholar and PubMed 'related articles'. We did not apply a diagnostic test search filter. We also searched reference lists and published review articles.  

SELECTION CRITERIA

We included studies in which all women from a given population had one or more index test(s) compared to a reference standard (either chromosomal verification or macroscopic postnatal inspection). Both consecutive series and diagnostic case-control study designs were included. Randomised trials where individuals were randomised to different screening strategies and all verified using a reference standard were also eligible for inclusion. Studies in which test strategies were compared head-to-head either in the same women, or between randomised groups were identified for inclusion in separate comparisons of test strategies. We excluded studies if they included less than five Down's syndrome cases, or more than 20% of participants were not followed up.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC meta-analytical methods or random-effects logistic regression methods to analyse test performance and compare test accuracy as appropriate. Analyses of studies allowing direct and indirect comparisons between tests were undertaken.

MAIN RESULTS

We included 56 studies (reported in 68 publications) involving 204,759 pregnancies (including 2113 with Down's syndrome). Studies were generally of good quality, although differential verification was common with invasive testing of only high-risk pregnancies. We evaluated 78 test combinations formed from combinations of 18 different tests, with or without maternal age; ADAM12 (a disintegrin and metalloprotease), AFP (alpha-fetoprotein), inhibin, PAPP-A (pregnancy-associated plasma protein A, ITA (invasive trophoblast antigen), free βhCG (beta human chorionic gonadotrophin), PlGF (placental growth factor), SP1 (Schwangerschafts protein 1), total hCG, progesterone, uE3 (unconjugated oestriol), GHBP (growth hormone binding protein), PGH (placental growth hormone), hyperglycosylated hCG, ProMBP (proform of eosinophil major basic protein), hPL (human placental lactogen), (free αhCG, and free ßhCG to AFP ratio. Direct comparisons between two or more tests were made in 27 studies.Meta-analysis of the nine best performing or frequently evaluated test combinations showed that a test strategy involving maternal age and a double marker combination of PAPP-A and free ßhCG significantly outperformed the individual markers (with or without maternal age) detecting about seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). Limited evidence suggested that marker combinations involving PAPP-A may be more sensitive than those without PAPP-A.

AUTHORS' CONCLUSIONS

Tests involving two markers in combination with maternal age, specifically PAPP-A, free βhCG and maternal age are significantly better than those involving single markers with and without age. They detect seven out of 10 Down's affected pregnancies for a fixed 5% FPR. The addition of further markers (triple tests) has not been shown to be statistically superior; the studies included are small with limited power to detect a difference.The screening blood tests themselves have no adverse effects for the woman, over and above the risks of a routine blood test. However some women who have a 'high risk' screening test result, and are given amniocentesis or chorionic villus sampling (CVS) have a risk of miscarrying a baby unaffected by Down's. Parents will need to weigh up this risk when deciding whether or not to have an amniocentesis or CVS following a 'high risk' screening test result.

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.

A systematic review of issues around antenatal screening and prenatal diagnostic testing for genetic disorders: women of Asian origin in western countries

Antenatal screening has become standard practice in many countries. However, not all pregnant women choose to be tested. In the UK, the incidence of some birth defects is found to be higher in babies of Asian women than in those of women from other ethnic groups, while there is some evidence suggesting that ethnic minorities, especially Asian women, are less likely to undergo antenatal screening and prenatal diagnosis, the reasons for which are unclear. This study aims to identify and describe the literature on issues around antenatal screening and prenatal diagnostic testing for genetic disorders among women of Asian descent in western countries. The Medline, CINAHL, ASSIA and PsycInfo databases were searched for the period of 1995 and 2010. Twenty-one studies met the inclusion criteria and were therefore reviewed. In general, Asian women were found to hold favourable attitudes towards testing. However, they reported a poorer understanding of testing than white women and not being offered a test, and were less able to make informed choices. Asian women in the UK and Australia were found to be less likely than their white counterparts to have undergone prenatal diagnosis, while such differences were not found in the USA and Canada. The equity of access to quality antenatal care, alongside comprehensive well thought out antenatal screening programmes, can be assured if strategies are in place which actively involve all ethnic groups and take account of social and cultural appropriateness for the population served. An understanding of broad factors that inform women's decision-making on test uptake would help health professionals provide women and their families with more culturally sensitive information and support that they may additionally need to make more informed choices.

Second trimester serum tests for Down's Syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 - or the specific area of chromosome 21 implicated in causing Down's syndrome - rather than two. It is the commonest congenital cause of mental retardation. Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  

OBJECTIVES

To estimate and compare the accuracy of second trimester serum markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to May 2007), EMBASE (1980 to 18 May 2007), BIOSIS via EDINA (1985 to 18 May 2007), CINAHL via OVID (1982 to 18 May 2007), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2007, Issue 1), MEDION (May 2007), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (May 2007), The National Research Register (May 2007), Health Services Research Projects in Progress database (May 2007). We studied reference lists and published review articles.  

SELECTION CRITERIA

Studies evaluating tests of maternal serum in women at 14-24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Fifty-nine studies involving 341,261 pregnancies (including 1,994 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Seventeen studies made direct comparisons between tests. Fifty-four test combinations were evaluated formed from combinations of 12 different tests and maternal age; alpha-fetoprotein (AFP), unconjugated oestriol (uE3), total human chorionic gonadotrophin (hCG), free beta human chorionic gonadotrophin (βhCG), free alpha human chorionic gonadotrophin (αhCG), Inhibin A, SP2, CA125, troponin, pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PGF) and proform of eosinophil major basic protein (ProMBP).Meta-analysis of 12 best performing or frequently evaluated test combinations showed double and triple tests (involving AFP, uE3, total hCG, free βhCG) significantly outperform individual markers, detecting six to seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate. Tests additionally involving inhibin performed best (eight out of every 10 Down's syndrome pregnancies) but were not shown to be significantly better than standard triple tests in direct comparisons. Significantly lower sensitivity occurred in women over the age of 35 years. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting the accuracy of the sensitivity.

AUTHORS' CONCLUSIONS

Tests involving two or more markers in combination with maternal age are significantly more sensitive than those involving one marker. The value of combining four or more tests or including inhibin have not been proven to show statistically significant improvement. Further study is required to investigate reduced test performance in women aged over 35 and the impact of differential pregnancy loss on study findings.

Ethnic differences in participation in prenatal screening for Down syndrome: a register-based study

OBJECTIVE

To assess ethnic differences in participation in prenatal screening for Down syndrome in the Netherlands.

METHODS

Participation in prenatal screening was assessed for the period 1 January 2009 to 1 July 2009 in a defined postal code area in the southwest of the Netherlands. Data on ethnic origin, socio-economic background and age of participants in prenatal screening were obtained from the Medical Diagnostic Centre and the Department of Clinical Genetics. Population data were obtained from Statistics Netherlands. Logistic regression models were used to assess ethnic differences in participation, adjusted for socio-economic and age differences.

RESULTS

The overall participation in prenatal screening was 3865 out of 15 093 (26%). Participation was 28% among Dutch women, 15% among those from Turkish ethnic origin, 8% among those from North-African origin, 15% among those from Aruban/Antillean origin and 26% among women from Surinamese origin.

CONCLUSIONS

Compared to Dutch women, those from Turkish, North-African, Aruban/Antillean and other non-Western ethnic origin were less likely to participate in screening. It was unexpected that women from Surinamese origin equally participated. It should be further investigated to what extent participation and non-participation in these various ethnic groups was based on informed decision-making.

Prenatal testing for Down syndrome: comparison of screening practices in the UK and USA

Prenatal testing for Down Syndrome is a topic covered in every genetic counselor's training as it constitutes the main workload of genetic counselors in prenatal settings. Most Western countries nowadays offer some type of testing for Down Syndrome. However, practices vary according to country with regards to what tests are offered, insurance coverage and the legal situation concerning the option of terminating an affected pregnancy. In view of the growing interest in international genetic counseling issues, this article aims to compare prenatal testing practices in two English-speaking countries: the United Kingdom and the United States of America. A case will be presented to highlight some of the differences in practice. The topic underlines important implications for genetic counseling practice, such as patients' understanding of testing practices, risk perception, counseling provision and impact of prenatal testing results.

Maternal serum screening for Down syndrome: are women’s perceptions changing?

OBJECTIVES

To document trends in serum screening for Down's syndrome.

BACKGROUND

Trends in the uptake of serum screening for Down syndrome have not been documented in a UK population.

DESIGN

A retrospective review of the rate of uptake in a unit that has offered serum screening for Down syndrome to all pregnant women.

SETTING

A large north of England hospital that has offered universal Down syndrome screening using the 'triple test' since 1992.

PATIENTS

A total of 47,998 women who booked for antenatal care.

MAIN OUTCOME MEASURES

Uptake of serum screening for Down syndrome.

METHODS

The results of the screening programme were contemporaneously recorded on a computer database, and the study team accessed the data.

RESULTS

There was a significant reduction in the uptake of serum screening for Down syndrome from a maximum of 82.6% in 1993 to 41.4% in 2005. There was a significant but small trend upwards in the age of women accepting screening and also a significant trend in the increase in the screen-positive rates.

CONCLUSIONS

The reduction in uptake of Down syndrome screening over the past 13 years must be taken into account when planning a screening programme. Other units should be encouraged to review their rate of uptake to determine if our data are representative of a wider trend.

Prevalence and predictors of receipt of prenatal information about genetic screening

OBJECTIVE

To examine the proportion of women who received information on genetic screening among those who had prenatal care and to determine whether the proportion varied by maternal characteristics.

METHODS

We used self-reported data from the Pregnancy Risk Assessment Monitoring System (PRAMS), a population-based survey of recent mothers, for birth years 2000-2002. Logistic regression was used to identify independent predictors of receiving information and to calculate adjusted prevalence ratios.

RESULTS

Among women who began prenatal care in the first trimester, 86% received information on genetic screening. The strongest predictors of receiving this information were completing the questionnaire in English and having military health insurance.

CONCLUSION

Most women receive information on prenatal genetic screening, but insurance status and language preference may impact women's access to this information.

Low uptake of prenatal screening for Down syndrome in minority ethnic groups and socially deprived groups: a reflection of women's attitudes or a failure to facilitate informed choices?

BACKGROUND

It is not known if lower uptake of prenatal screening for Down syndrome in women from minority ethnic groups and socioeconomically disadvantaged women reflects more negative attitudes towards undergoing the test or women not acting in line with their attitudes i.e. not making an informed choice.

METHODS

Uptake of prenatal screening, attitudes towards undergoing the test, uptake-attitude consistency, and informed choice were assessed in a prospective study of 1499 pregnant women attending two UK hospitals.

RESULTS

Uptake was higher in white and socioeconomically advantaged women than in other women. There were no differences in attitudes towards undergoing the test; all women expressed relatively positive attitudes. Uptake-attitude consistency was higher in white and socioeconomically advantaged women than others, particularly in those with positive attitudes towards undergoing the test (76% white women with positive attitudes had the test compared with 45% South Asian women [difference 31%, 95% confidence interval (95% CI) 18-43] and 78% socioeconomically advantaged women compared with 63% more disadvantaged women (difference 15%, 95% CI 7-24)). Controlling for demographic variables, South Asian and socioeconomically disadvantaged women with positive attitudes were less likely to make an informed choice than other women [odds ratio (OR) 0.22, 95% CI 0.10-0.45 and OR 0.62, 95% CI 0.41-0.93, respectively].

CONCLUSION

Lower uptake of screening for Down syndrome in women from minority ethnic groups and socioeconomically disadvantaged women does not reflect more negative attitudes towards screening but rather lower rates of informed choice, as assessed in this study. Healthcare systems appear to facilitate informed choices in the context of prenatal screening for Down syndrome screening less well for women from minority ethnic groups and those who are socioeconomically disadvantaged than for other women.

A look at a Hispanic and African American population in an urban prenatal diagnostic center: Referral reasons, amniocentesis acceptance, and abnormalities detected

PURPOSE

To describe the Hispanic and African-American population referred to our inner city Los Angeles Prenatal Diagnostic Center. To evaluate trends in referral reasons, amniocentesis acceptance, and to assess the number and types of fetal abnormalities found from 1995 to 2001.

METHODS

A retrospective study using the data from 3085 daily log entries on patients referred for prenatal counseling. The data included race, age, referral reason, amniocentesis decision and results, and fetal abnormalities.

RESULTS

The population was 76% Hispanic and 22% African American. Most referrals were for advanced maternal age (42%) and maternal serum screening (28%). The overall amniocentesis acceptance rate was 52%; advanced maternal age amniocentesis acceptance rate was 46%, and maternal serum screen positive amniocentesis acceptance rate was significantly higher at 64%. There was a significant difference between the overall amniocentesis acceptance rate for Hispanics (48%) and African Americans (63%). There was also a significant downward trend in amniocentesis acceptance between 1995 (63%) and 2001 (39%). Amniocentesis acceptance was significantly greater among patients who were < 35 years of age (65%) than those who were older (47%). An incidence of 7% abnormalities was detected by ultrasound and amniocentesis.

CONCLUSIONS

Acceptance of amniocentesis in the Hispanic and African American population in our prenatal diagnostic center is significantly lower than what has previously been reported in the literature for Caucasians and reported in California statewide prenatal diagnostic center data for non-MS-AFP. There was a significant decline in amniocentesis acceptance from 1995 to 2001. Our incidence of fetal abnormalities was higher than reported in California statewide data.

Social and ethnic inequalities in the offer and uptake of prenatal screening and diagnosis in the UK: a systematic review

OBJECTIVE

To review studies addressing the question of whether there are social inequalities in either the offer or the uptake of prenatal testing in the UK.

METHOD

Systematic review of studies assessing the offer or uptake of prenatal screening or diagnosis according to social class or ethnic origin. Electronic databases were searched using a strategy developed for a review of inequalities in access to maternity care supplemented with terms specific to prenatal testing. Further papers were identified from reference lists, citation searches and key organizations.

RESULTS

From over 600 identified papers, 41 were potentially relevant. Twenty met the inclusion criteria. The studies included covered screening and/or diagnosis for Down's syndrome, neural tube defects, haemoglobin disorders and HIV. Many studies were limited by small numbers or poor reporting of data and analysis. Six studies reported data on prenatal testing according to women's social class or educational level. None found any significant social inequalities in testing. Some studies suggested that women of South Asian origin might be up to 70% less likely to receive prenatal testing for haemoglobin disorders and Down's syndrome than White women. A small number of studies suggested that South Asian women might be less likely to be offered testing.

CONCLUSIONS

This review provides some evidence of ethnic inequalities in access to prenatal testing. Further research is required to improve our understanding of why testing may not be offered, the reasons for failure to take up testing when offered, and to identify whether there are other social inequalities in access to prenatal testing.

The use of record linkage for auditing the uptake and outcome of prenatal serum screening and prenatal diagnostic tests for Down syndrome

OBJECTIVES

To pilot the use of linked routine records for auditing Down syndrome prenatal serum screening and diagnostic tests.

METHODS

The cohort studied were 110 272 patients of 4 London maternity units that offered the Bart's maternal serum tests any time between 1990 and 1999. Audit was based on linked data derived from obstetric records, referral data on maternal serum screening and/or prenatal diagnoses. Cytogenetic reports without matching obstetric data were retained in the cohort as they included fetal deaths or terminations.

RESULTS

(1) Significant independent influences on uptake of serum screening (58% overall) were maternal age, ethnicity, year and referring hospital, and those on uptake of prenatal diagnosis (4% overall) were screening result (54% uptake after positive screen), maternal age, year and referring hospital; (2) detection, false-positive rates and odds of being affected after positive results were respectively 49%, 4% and 1 : 59 between 1990 and 1994, and 78%, 7% and 1 : 58 after 1994. Using maternal age alone (cut-off > or =37 at delivery), these would have been respectively 40%, 7% and 1 : 96 between 1990 and 1994, and 40%, 9% and 1 : 107 between 1995 and 1999.

CONCLUSIONS

Ongoing audit of DS prenatal programmes could be derived from computerised maternity data sets if they included fetal deaths, and relevant laboratory and ultrasound findings.