Prevalence of Down's Syndrome in England, 1998-2013: Comparison of linked surveillance data and electronic health records

INTRODUCTION

Disease registers and electronic health records are valuable resources for disease surveillance and research but can be limited by variation in data quality over time. Quality may be limited in terms of the accuracy of clinical information, of the internal linkage that supports person-based analysis of most administrative datasets, or by errors in linkage between multiple datasets.

OBJECTIVES

By linking the National Down Syndrome Cytogenetic Register (NDSCR) to Hospital Episode Statistics for England (HES), we aimed to assess the quality of each and establish a consistent approach for analysis of trends in prevalence of Down's syndrome among live births in England.

METHODS

Probabilistic record linkage of NDSCR to HES for the period 1998-2013 was supported by linkage of babies to mothers within HES. Comparison of prevalence estimates in England were made using NDSCR only, HES data only, and linked data. Capture-recapture analysis and quantitative bias analysis were used to account for potential errors, including false positive diagnostic codes, unrecorded diagnoses, and linkage error.

RESULTS

Analyses of single-source data indicated increasing live birth prevalence of Down's Syndrome, particularly in the analysis of HES. Linked data indicated a contrastingly stable prevalence of 12.3 (plausible range: 11.6-12.7) cases per 10 000 live births.

CONCLUSION

Case ascertainment in NDSCR improved slightly over time, creating a picture of slowly increasing prevalence. The emerging epidemic suggested by HES primarily reflects improving linkage within HES (assignment of unique patient identifiers to hospital episodes). Administrative data are valuable but trends should be interpreted with caution, and with assessment of data quality over time. Data linkage with quantitative bias analysis can provide more robust estimation and, in this case, stronger evidence that prevalence is not increasing. Routine linkage of administrative and register data can enhance the value of each.

Estimating the birth prevalence and pregnancy outcomes of congenital malformations worldwide

Congenital anomaly registries have two main surveillance aims: firstly to define baseline epidemiology of important congenital anomalies to facilitate programme, policy and resource planning, and secondly to identify clusters of cases and any other epidemiological changes that could give early warning of environmental or infectious hazards. However, setting up a sustainable registry and surveillance system is resource-intensive requiring national infrastructure for recording all cases and diagnostic facilities to identify those malformations that that are not externally visible. Consequently, not all countries have yet established robust surveillance systems. For these countries, methods are needed to generate estimates of prevalence of these disorders which can act as a starting point for assessing disease burden and service implications. Here, we describe how registry data from high-income settings can be used for generating reference rates that can be used as provisional estimates for countries with little or no observational data on non-syndromic congenital malformations.

EUROCAT: an update on its functions and activities

This paper provides an outline of the development and growth of EUROCAT, the European network of congenital anomaly registers. In recent years the network has been through a period of transition and change. The Central Register of data has transferred from the Ulster University to the EU Joint-Research-Centre, Ispra, Italy.The benefits of combining data from across Europe, from different populations and countries are described by the uses to which these data can be put. These uses include:. surveillance of anomalies at a local, regional or pan-European level. pharmacovigilance. registration of rare diseasesNew studies and projects are underway, including EUROlinkCAT (a Horizon 2020 funded data-linkage project), promising a fruitful future in further research of congenital anomalies.

Mortality from aortic stenosis: prospective study of serum calcium and phosphate

PURPOSE

To investigate the associations between levels of serum calcium and phosphate and subsequent death from aortic stenosis, and the implications for prevention.

METHODS

A prospective (nested case-control) analysis of serum calcium and phosphate levels was performed in stored samples from the British United Provident Association prospective study of 21 520 men aged 35-64, followed for up to 32 years. There were 49 men without baseline valvular heart disease who subsequently died of aortic stenosis. Each was matched, for age, duration of sample storage and number of freeze-thaw cycles, with four unaffected control subjects. Odds ratios for death from aortic stenosis were estimated by logistic regression.

RESULTS

Mean serum calcium concentration was higher in men who died of aortic stenosis than in those who did not (2.44 vs. 2.39 mmol L^-1 ; P = 0.01). The risk of death from aortic stenosis in the highest calcium tertile was 2.87-fold higher than in the lowest tertile (95% confidence interval 1.22-6.76). There was a continuous dose-response relationship; risk of death from aortic stenosis increased by 51% (11-105%) per 0.1 mmol L^-1 increase in serum calcium, equivalent to a 34% (10-52%) lower risk per 0.1 mmol L^-1 decrease. Serum phosphate was not significantly higher in men who died of aortic stenosis than in those who did not (1.0 vs. 0.99 mmol L^-1 ; P = 0.76).

CONCLUSIONS

The association between serum calcium and subsequent mortality from aortic stenosis is of potential preventive significance. If confirmed quantitatively in other similar cohort studies, the results suggest that a very small reduction in serum calcium (about 5%) could translate into a large (about one-third) reduction in aortic stenosis.

The association between Ehlers-Danlos syndrome-hypermobility type and gastrointestinal symptoms in university students: a cross-sectional study

BACKGROUND

Patients with Ehlers-Danlos syndrome-hypermobility type (EDS-HT) have increased prevalence of gastrointestinal (GI) symptoms, particularly reflux and dyspepsia. EDS-HT is associated with dysautonomia, psychopathology, and chronic pain which can be associated with GI symptoms. The association between GI symptoms and EDS-HT in a 'non-patient' population and the effect of the above-mentioned factors has never been studied.

METHODS

In a cross sectional study, a hypermobility questionnaire was used to screen university students; further clinical examination established the diagnosis of EDS-HT. Validated questionnaires assessed for GI, somatic, pain and autonomic symptoms, psychopathology and quality of life (QOL). These were compared in students with and without EDS-HT; logistic regression analysis examined associations between EDS-HT, GI symptoms and other variables.

KEY RESULTS

Of 1998 students screened, 162 were included: 74 EDS-HT (21.0 years, 53% female) vs 88 Non-EDS-HT (21.5 years, 65% female). Compared to non-EDS-HT students, EDS-HT students were more likely to have multiple GI symptoms (41.9% vs 27.3% P=.05), particularly postprandial fullness (34.4% vs 15.9%, P=.01) and early satiety (32% vs 17%, P=.03), greater autonomic (P<.001) and somatic symptoms (P=.04) but not psychopathology (P>.8). The association between EDS-HT and postprandial symptoms was dependent on autonomic factors but independent of pain and psychopathology. Pain-related QOL scores were reduced in the EDS-HT group (80 vs 90, P=.03).

CONCLUSIONS AND INFERENCES

The previously described association between EDS-HT, dyspepsia, pain and autonomic symptoms in patients is also present in non-patient groups. Future studies are necessary to explore the etiological role of connective tissue in GI and extra intestinal symptoms.

Validation plots in antenatal screening for Down's syndrome

Objective

To validate empirically the accuracy of antenatal Down's syndrome screening using the Integrated test, to compare this with other screening tests (including the Integrated test with the addition of cross trimester [CT] marker ratios) and to suggest how such validation analyses should be presented and interpreted.

Methods

Using data from 7809 unaffected and 27 Down's syndrome pregnancies that had had an Integrated test, risk estimates for various screening tests (maternal age, Double, Triple, Quadruple, Combined, Integrated and serum Integrated tests) that use Integrated test markers were categorized according to quintile categories of risk estimates of the 27 affected pregnancies. For each screening test, the median risk estimate for each category was plotted against the observed prevalence within each category. Such validation plots were also produced for the Integrated test with CT marker ratios by measuring the level of the serum markers in the trimester of pregnancy not already measured in stored samples of all affected and a one-in-five sample of unaffected pregnancies. The robustness of the method was assessed by repeating the analysis for the Integrated test after re-classifying affected pregnancies with low risk estimates as unaffected, simulating the underascertainment of cases.

Results

The validation plots (i) confirmed the accuracy of risk estimation for the different tests (by how close the points lay to the line of identity between predicted risk and observed prevalence), (ii) demonstrated the differences in screening performance of the different tests (by the range of risk spanned by the points and, in particular, the separation between the points representing the lowest risk and the next point), and (iii) are robust to underascertainment of affected pregnancies (by having little influence on the closeness of the points to the line of identity).

Conclusion

The validation plot is a useful, simple and robust way to assess the validity of new screening methods, to assess the accuracy of risk estimation and to audit the performance of screening programmes.

Prevention of neural tube defects in the UK: a missed opportunity

OBJECTIVE

In 1991, the Medical Research Council (MRC) Vitamin Study demonstrated that folic acid taken before pregnancy and in early pregnancy reduced the risk of a neural tube defect (NTD). We aimed to estimate the number of NTD pregnancies that would have been prevented if flour had been fortified with folic acid in the UK from 1998 as it had been in the USA.

DESIGN

Estimates of NTD prevalence, the preventive effect of folic acid and the proportion of women taking folic acid supplements before pregnancy were used to predict the number of NTD pregnancies that would have been prevented if folic acid fortification had been implemented.

SETTING

Eight congenital anomaly registers in England and Wales.

MAIN OUTCOME MEASURES

The prevalence of pregnancies with an NTD in the UK and the number of these pregnancies that would have been prevented if folic acid fortification had been implemented.

RESULTS

From 1991 to 2012, the prevalence of NTD pregnancies was 1.28 (95% CI 1.24 to 1.31) per 1000 total births (19% live births, 81% terminations and 0.5% stillbirths and fetal deaths ≥20 weeks' gestation). If the USA levels of folic acid fortification from 1998 onwards had been adopted in the UK, an estimated 2014 fewer NTD pregnancies would have occurred.

CONCLUSIONS

Failure to implement folic acid fortification in the UK has caused, and continues to cause, avoidable terminations of pregnancy, stillbirths, neonatal deaths and permanent serious disability in surviving children.

Estimating the risk of Down's syndrome in antenatal screening and the gestation at which this risk applies

Two equations are given to estimate the risk of a woman having a Down's syndrome pregnancy according to maternal age: one for use in estimating antenatal screening performance and the other for use in estimating an individual woman's risk of having an affected pregnancy. Because Down's syndrome pregnancies have an increased tendency to result in a spontaneous fetal loss, the estimation of a woman's risk of having an affected pregnancy will be dependent on gestational age. The best estimates of the prevalence of Down's syndrome are obtained from information relating to births and can reliably be adjusted to prevalence in early second trimester. The most reliable estimates of risk of a Down's syndrome pregnancy using all the currently used markers apply to early in the second trimester. These risks cannot accurately be adjusted to apply to term, because the first trimester markers have not in general been studied in pregnancies that continue to term. Therefore the early second trimester of pregnancy is the gestational age at which all screening performances should be given for the different antenatal screening programmes for Down's syndrome.

The Performance of Blood Pressure and other Cardiovascular Risk Factors as Screening Tests for Ischaemic Heart Disease and Stroke

This paper summarises the main evidence and conclusions relating to using blood pressure measurement as a screening test to identify people who will develop ischaemic heart disease (IHD) or stroke, as recently published in a Health Technology Assessment report1. While blood pressure is recognised as an important cause of stroke and IHD, and lowering blood pressure can substantially lower the risk of these diseases, the measurement of blood pressure is a poor screening test. It is not good in distinguishing those who will and will not develop these diseases. The poor screening performance is illustrated by the findings that in the largest cohort study, persons in the top 10% of the distribution of systolic blood pressure experienced only 21% of all IHD events and 28% of all strokes at a given age. Using several cardiovascular risk factors in combination does not add materially to the poor screening performance of blood pressure alone. Among persons in a specified age group, the 5% at highest risk experience 17% of all heart disease deaths with risk computation based on blood pressure alone, 22% when based on blood pressure and apolipoprotein B (or LDL cholesterol) in combination, and only 28% using these two, smoking and three other cardiovascular risk factors all in combination. Identifying patients at the time of hospital discharge following myocardial infarction or stroke is the most effective screening test to identify those who will die of cardiovascular disease. In patients with a history of myocardial infarction or stroke the cardiovascular death rate in the absence of treatment is about 5% per year, a risk that persists for at least 15 years. In the absence of treatment, about half of all deaths from heart disease in a population occur after hospital discharge following the first infarct. Among persons with no history of cardiovascular disease, age is a better screening test than the reversible risk factors, and the best policy is to offer treatment to all persons above a specified age such as 55 years.

Prevalence of neural tube defect pregnancies in England and Wales from 1964 to 2004

Objectives: To determine the prevalence of pregnancies with a neural tube defect (NTD) in England and Wales between 1964 and 2004 and to estimate the relative impact of antenatal screening and a change in the incidence of these defects on the prevalence of births with NTDs.

Settings: Use of data published by the Office for National Statistics (ONS) on terminations of pregnancies with an NTD and births with an NTD from 1964 to 2004.

Methods: Estimates were made of the total number of terminations of pregnancies and births with an NTD by taking account of the under-reporting of these terminations and births using a previously described method. In 1995 ONS started to report the number of terminations with an NTD rather than the total numbers of terminations with a central nervous system (CNS) malformation that had previously been used to estimate the number of NTD terminations. Adjustment was made for this and new estimates of the total number of NTD pregnancies were produced to 2004.

Results: There were an estimated 969 pregnancies with NTDs (168 (17%) births and 801(83%) terminations) in England and Wales in 2004. An estimated 44% of NTD terminations and 32% of births were not reported as such. The birth prevalence per 1000 decreased fallen 93% from 3.6 in 1964 to 0.3 in 2004, 59% due to an underlying decrease in the prevalence of NTDs and 34% due to screening diagnosis and subsequent termination of affected pregnancies.

Conclusion: The prevalence of NTD pregnancies decreased by around two per 1000 from 1964 to 1990 and thereafter remained fairly constant. The prevalence of NTD pregnancies is substantially underestimated if it is based only on reported NTD births (by 88%) and also if it is based on reported NTD births and terminations (by 52%), because most NTD pregnancies in England and Wales are terminated following antenatal screening and most of these terminations are not reported.

Graphical presentation of distributions of risk in screening

Objective: The screening performance of tests involving multiple markers is usually presented visually as two Gaussian relative frequency distributions of risk, one curve relating to affected and the other to unaffected individuals. If the distribution of the underlying screening markers is approximately Gaussian, risk estimates based on the same markers will usually also be approximately Gaussian. However, this approximation sometimes fails. Here we examine the circumstances when this occurs.

Setting: A theoretical statistical analysis.

Methods: Hypothetical log Gaussian relative distributions of affected and unaffected individuals were generated for three antenatal screening markers for Down's syndrome. Log likelihood ratios were calculated for each marker value and plots of the relative frequency distributions were compared with plots of Gaussian distributions based on the means and standard deviations of these log likelihood ratios.

Results: When the standard deviations of the distributions of a perfectly Gaussian screening marker are similar in affected and unaffected individuals, the distributions of risk estimates are also approximately Gaussian. If the standard deviations differ materially, incorrectly assuming that the distributions of the risk estimates are Gaussian creates a graphical anomaly in which the distributions of risk in affected and unaffected individuals plotted on a continuous risk scale intersect in two places. This is theoretically impossible. Plotting the risk distributions empirically reveals that all individuals have an estimated risk above a specified value. For individuals with more extreme marker values, the risk estimates reverse and increase instead of continuing to decrease.

Conclusion: It is useful to check whether a Gaussian approximation for the distribution of risk estimates based on a screening marker is valid. If the value of the marker level at which risk reversal occurs lies within the set truncation limits, these may need to be reset, and a Gaussian model may be inappropriate to illustrate the risk distributions.

The effect of correlations between screening markers on screening performance

Objectives: It is widely thought that correlations between screening markers will tend to degrade screening performance. We performed a computer simulation study to investigate the quantitative effect of correlations between two markers on screening performance, using prenatal screening for Down's syndrome as an example, although the results apply generally.

Methods: Monte Carlo simulation was used to generate values of two hypothetical markers, A and B, in 1000 affected and 1000 unaffected pregnancies. The means, standard deviations and correlations of A and B were varied in five different examples.

Results: If markers A and B are, on average, higher in affected than unaffected pregnancies and each marker, individually, has the same detection rate for a given false-positive rate (i.e. the same screening performance), then the screening performance of A and B together tends to decrease as A and B become more positively correlated with each other (within affected or unaffected categories) and tends to increase as A and B become more negatively correlated. If A is, on average, higher in affected pregnancies and B is, on average, lower in affected pregnancies (but again each marker has the same screening performance), the opposite pattern is observed; screening performance increases as A and B become more positively correlated and screening performance decreases as they become more negatively correlated. If A and B have unequal screening performances, modest correlations between A and B have little effect on the screening performance of A and B together, but when the correlations are strong whether positive or negative (with r values greater than about 0.45 or less than −0.45) screening performance progressively increases.

Conclusion: Correlations between screening markers considered separately in affected and unaffected pregnancies can either decrease or increase screening performance. In practice, these effects are usually modest, because most screening markers are not highly correlated with each other and the effects become important only with strong correlations, whether positive or negative.

Functional gastrointestinal disorders are associated with the joint hypermobility syndrome in secondary care: a case-control study

BACKGROUND

The overlap of unexplained gastrointestinal (GI) and somatic symptoms is well established in patients with functional gastrointestinal disorders (FGID). Joint hypermobility syndrome (JHS) is a non-inflammatory connective tissue disorder associated with GI and somatic symptoms. We aimed to determine whether there is an association between diagnosis of JHS and FGID and the impact of this association on comorbidities and quality of life (QOL).

METHODS

Prospective case-control study in secondary care GI clinics over 2 years. JHS was assessed by the first author prior to consultation in 641 consecutive new patients. Diagnosis of FGID (cases, n = 336) or organic disorders (controls, n = 305) was established blind to JHS status. JHS prevalence was compared in cases (FGID patients) and controls (organic disorders patients). Extra-intestinal comorbidity and QOL were compared in FGID patients with and without JHS.

KEY RESULTS

JHS prevalence was higher in FGID compared to organic GI disorders (39.0% vs 27.5%, ORadj: 1.51, CI: 1.07-2.12, p = 0.02), and particularly associated with functional gastroduodenal disorders (44.1%, ORadj: 2.08, CI: 1.25-3.46, p = 0.005), specifically postprandial distress syndrome (51%, ORadj: 1.99, CI: 1.06-3.76, p = 0.03). FGID patients with JHS had increased chronic pain (23.2% vs 11.9%, p = 0.01), fibromyalgia (10.5% vs 3.1%, p = 0.01), somatization scores (13 vs 10, p < 0.001), urinary autonomic scores (30.5 vs 20.7, p = 0.03), and worse pain-related QOL scores (45.0 vs 63.5, p = 0.004).

CONCLUSIONS & INFERENCES

JHS is significantly associated with FGID, and this subgroup of patients have increased comorbidity and decreased QOL. Further research is required to understand the pathophysiological basis of this association.

In vivo and in vitro ketamine exposure exhibits a dose-dependent induction of activity-dependent neuroprotective protein in rat neurons

Anesthetic doses of ketamine induce apoptosis, as well as gene expression of activity-dependent neuroprotective protein (ADNP), a putative homeodomain transcription factor in rat pups (P7). This study investigated if ketamine induced ADNP protein in a dose-dependent manner in vitro and in vivo using primary cultures of cortical neurons and neonatal pups (P7). In vivo immunohistochemistry demonstrated a sub-anesthetic dose of ketamine increased ADNP in the somatosensory cortex (SCC) which was previously identified to be damaged by repeated exposure to anesthetic doses of ketamine. Administration of low-dose ketamine prior to full sedation prevented caspase-3 activation in the hippocampus and SCC. Primary cultures of cortical neurons treated with ketamine (10 μM-10mM) at 3 days-in vitro (3 DIV) displayed a concentration-dependent decrease in expanded growth cones. Furthermore, neuronal production and localization of ADNP varied as a function of both ketamine concentration and length of exposure. Taken together, these data support the model that ADNP induction may be partially responsible for the efficacy of a low-dose ketamine pre-treatment in preventing ketamine-induced neuronal cell death.

Insulin resistance and gray matter volume in neurodegenerative disease

The goal of this study was to compare insulin resistance in aging and aging-related neurodegenerative diseases, and to determine the relationship between insulin resistance and gray matter volume (GMV) in each cohort using an unbiased, voxel-based approach. Insulin resistance was estimated in apparently healthy elderly control (HC, n=21) and neurodegenerative disease (Alzheimer's disease (AD), n=20; Parkinson's disease (PD), n=22) groups using Homeostasis Model Assessment of Insulin Resistance 2 (HOMA2) and intravenous glucose tolerance test (IVGTT). HOMA2 and GMV were assessed within groups through General Linear Model multiple regression. We found that HOMA2 was increased in both AD and PD compared to the HC group (HC vs. AD, p=0.002, HC vs. PD, p=0.003), although only AD subjects exhibited increased fasting glucose (p=0.005). Furthermore, our voxel-based morphometry analysis revealed that HOMA2 was related to GMV in all cohorts in a region-specific manner (p<0.001, uncorrected). Significant relationships were observed in the medial prefrontal cortex (HC), medial temporal regions (AD), and parietal regions (PD). Finally, the directionality of the relationship between HOMA2 and GMV was disease-specific. Both HC and AD subjects exhibited negative relationships between HOMA2 and brain volume (increased HOMA2 associated with decreased brain volume), while a positive relationship was observed in PD. This cross-sectional study suggests that insulin resistance is increased in neurodegenerative disease, and that individuals with AD appear to have more severe metabolic dysfunction than individuals with PD or PD dementia.

Prevalence and risk of Down syndrome in monozygotic and dizygotic multiple pregnancies in Europe: implications for prenatal screening

OBJECTIVE

To determine risk of Down syndrome (DS) in multiple relative to singleton pregnancies, and compare prenatal diagnosis rates and pregnancy outcome.

DESIGN

Population-based prevalence study based on EUROCAT congenital anomaly registries.

SETTING

Eight European countries.

POPULATION

14.8 million births 1990-2009; 2.89% multiple births.

METHODS

DS cases included livebirths, fetal deaths from 20 weeks, and terminations of pregnancy for fetal anomaly (TOPFA). Zygosity is inferred from like/unlike sex for birth denominators, and from concordance for DS cases.

MAIN OUTCOME MEASURES

Relative risk (RR) of DS per fetus/baby from multiple versus singleton pregnancies and per pregnancy in monozygotic/dizygotic versus singleton pregnancies. Proportion of prenatally diagnosed and pregnancy outcome.

STATISTICAL ANALYSIS

Poisson and logistic regression stratified for maternal age, country and time.

RESULTS

Overall, the adjusted (adj) RR of DS for fetus/babies from multiple versus singleton pregnancies was 0.58 (95% CI 0.53-0.62), similar for all maternal ages except for mothers over 44, for whom it was considerably lower. In 8.7% of twin pairs affected by DS, both co-twins were diagnosed with the condition. The adjRR of DS for monozygotic versus singleton pregnancies was 0.34 (95% CI 0.25-0.44) and for dizygotic versus singleton pregnancies 1.34 (95% CI 1.23-1.46). DS fetuses from multiple births were less likely to be prenatally diagnosed than singletons (adjOR 0.62 [95% CI 0.50-0.78]) and following diagnosis less likely to be TOPFA (adjOR 0.40 [95% CI 0.27-0.59]).

CONCLUSIONS

The risk of DS per fetus/baby is lower in multiple than singleton pregnancies. These estimates can be used for genetic counselling and prenatal screening.

Effects of unilateral nigrostriatal dopamine depletion on peripheral glucose tolerance and insulin signaling in middle aged rats

Clinical studies indicate an increased incidence of impaired glucose tolerance in individuals with Parkinson's disease (PD). The mechanisms that underlie this co-morbidity are currently unknown. The purpose of this study was to analyze peripheral glucose tolerance following severe unilateral nigrostriatal dopamine (DA) depletion, and to determine whether central and peripheral insulin signaling was affected in the 6-hydroxydopamine (6-OHDA) middle-aged rat model of PD. Although serum insulin levels differed significantly between the 6-OHDA and sham groups over the course of a glucose tolerance test six weeks post-lesion, no significant effect on glucose tolerance or insulin signaling in skeletal muscle was observed. In contrast, markers of striatal insulin resistance were evident in the rats. These data suggest that while 6-OHDA may affect serum insulin levels and striatal insulin signaling, the unilateral 6-OHDA lesion model does not induce glucose intolerance or peripheral insulin resistance, at least at the six-week post-lesion timepoint.

Insulin resistance impairs nigrostriatal dopamine function

Clinical studies have indicated a link between Parkinson's disease (PD) and Type 2 Diabetes. Although preclinical studies have examined the effect of high-fat feeding on dopamine function in brain reward pathways, the effect of diet on neurotransmission in the nigrostriatal pathway, which is affected in PD and parkinsonism, is less clear. We hypothesized that a high-fat diet, which models early-stage Type 2 Diabetes, would disrupt nigrostriatal dopamine function in young adult Fischer 344 rats. Rats were fed a high fat diet (60% calories from fat) or a normal chow diet for 12 weeks. High fat-fed animals were insulin resistant compared to chow-fed controls. Potassium-evoked dopamine release and dopamine clearance were measured in the striatum using in vivo electrochemistry. Dopamine release was attenuated and dopamine clearance was diminished in the high-fat diet group compared to chow-fed rats. Magnetic resonance imaging indicated increased iron deposition in the substantia nigra of the high fat group. This finding was supported by alterations in the expression of several proteins involved in iron metabolism in the substantia nigra in this group compared to chow-fed animals. The diet-induced systemic and basal ganglia-specific changes may play a role in the observed impairment of nigrostriatal dopamine function.

Down's syndrome: screening and antenatal diagnosis regionally in England and Wales 1989–2008

Objective

To illustrate regional changes that occurred in screening for Down's syndrome (trisomy 21) in England and Wales from 1989 to 2008.

Methods

The National Down Syndrome Cytogenetic Register has collected data on all ante- and postnatal diagnoses of Down's syndrome in England and Wales since 1989 ( n = 27,954). The percentages of (i) diagnoses made antenatally, (ii) antenatal diagnoses that had nuchal translucency (NT) measured, and (iii) antenatal diagnoses in mothers aged 37 and over with advanced maternal age as the sole recorded indication for diagnosis are presented according to where the mother lived (Government Office Region), year of diagnosis (1989–1994, 1995–2000, 2001–2006, 2007–2008), and maternal age (<37 years, ≥37 years).

Results

The percentage of cases diagnosed antenatally has increased in younger women but varies between regions. It remained relatively constant at approximately 70% in older women. The use of NT measurement in antenatal screening has expanded rapidly but varies regionally, being most common in London and the South East where, in 2007–2008, over 75% of antenatal diagnoses in older women had NT measured. The sole indication of advanced maternal age has substantially reduced, and was less than 10% in older mothers in all regions in 2007–2008.

Conclusions

There are regional and maternal age variations in Down's syndrome screening and diagnosis. Some regions used NT measurements, and eliminated advanced maternal age as sole reason for antenatal diagnostic testing more quickly than others. The reasons for variations need to be identified and addressed to ensure that when new screening techniques become available, regional differences are minimized.

Case-control analysis of paternal age and trisomic anomalies

OBJECTIVES

To determine whether older paternal age increases the risk of fathering a pregnancy with Patau (trisomy 13), Edwards (trisomy 18), Klinefelter (XXY) or XYY syndrome.

DESIGN

Case-control: cases with each of these syndromes were matched to four controls with Down syndrome from within the same congenital anomaly register and with maternal age within 6 months.

SETTING

Data from 22 EUROCAT congenital anomaly registers in 12 European countries.

PARTICIPANTS

Diagnoses with observed or (for terminations) predicted year of birth from 1980 to 2005, comprising live births, fetal deaths with gestational age ≥ 20 weeks and terminations after prenatal diagnosis of the anomaly. Data include 374 cases of Patau syndrome, 929 of Edwards syndrome, 295 of Klinefelter syndrome, 28 of XYY syndrome and 5627 controls with Down syndrome.

MAIN OUTCOME MEASURES

Odds ratio (OR) associated with a 10-year increase in paternal age for each anomaly was estimated using conditional logistic regression. Results were adjusted to take account of the estimated association of paternal age with Down syndrome (1.11; 95% CI 1.01 to 1.23).

RESULTS

The OR for Patau syndrome was 1.10 (95% CI 0.83 to 1.45); for Edwards syndrome, 1.15 (0.96 to 1.38); for Klinefelter syndrome, 1.35 (1.02 to 1.79); and for XYY syndrome, 1.99 (0.75 to 5.26).

CONCLUSIONS

There was a statistically significant increase in the odds of Klinefelter syndrome with increasing paternal age. The larger positive associations of Klinefelter and XYY syndromes with paternal age compared with Patau and Edwards syndromes are consistent with the greater percentage of these sex chromosome anomalies being of paternal origin.

Maternal age-specific risk of non-chromosomal anomalies

OBJECTIVES

To determine the excess risk of non-chromosomal congenital anomaly (NCA) among teenage mothers and older mothers.

DESIGN AND SETTING

Population-based prevalence study using data from EUROCAT congenital anomaly registers in 23 regions of Europe in 15 countries, covering a total of 1.75 million births from 2000 to 2004.

PARTICIPANTS

A total of 38,958 cases of NCA that were live births, fetal deaths with gestational age > or = 20 weeks or terminations of pregnancy following prenatal diagnosis of a congenital anomaly.

MAIN OUTCOME MEASURES

Prevalence of NCA according to maternal age, and relative risk (RR) of NCA and 84 standard NCA subgroups compared with mothers aged 25-29.

RESULTS

The crude prevalence of all NCA was 26.5 per 1000 births in teenage mothers (<20 years), 23.8 for mothers 20-24 years, 22.5 for mothers 25-29 years, 21.5 for mothers 30-34 years, 21.4 for mothers 35-39 years and 22.6 for mothers 40-44 years. The RR adjusted for country for teenage mothers was 1.11 (95% CI 1.06-1.17); 0.99 (95% CI 0.96-1.02) for mothers 35-39; and 1.01 (95% CI 0.95-1.07) for mothers 40-44. The pattern of maternal age-related risk varied significantly between countries: France, Ireland and Portugal had higher RR for teenage mothers, Germany and Poland had higher RR for older mothers. The maternal age-specific RR varied for different NCAs. Teenage mothers were at a significantly greater risk (P < 0.01) of gastroschisis, maternal infection syndromes, tricuspid atresia, anencephalus, nervous system and digestive system anomalies while older mothers were at a significantly greater risk (P < 0.01) of fetal alcohol syndrome, encephalocele, oesophageal atresia and thanatophoric dwarfism.

CONCLUSIONS

Clinical and public health interventions are needed to reduce environmental risk factors for NCA, giving special attention to young mothers among whom some risk factors are more prevalent. Reassurance can be given to older mothers that their age in itself does not confer extra risk for NCA.

Use of blood pressure lowering drugs in the prevention of cardiovascular disease: meta-analysis of 147 randomised trials in the context of expectations from prospective epidemiological studies

OBJECTIVES

To determine the quantitative efficacy of different classes of blood pressure lowering drugs in preventing coronary heart disease (CHD) and stroke, and who should receive treatment.

DESIGN

Meta-analysis. Data source Medline (1966-2007).

STUDY SELECTION

Randomised trials of blood pressure lowering drugs recording CHD events and strokes. 108 trials studied differences in blood pressure between study drug and placebo (or control group not receiving the study drug) ("blood pressure difference trials"), and 46 trials compared drugs ("drug comparison trials"). Seven trials with three randomised groups fell into both categories. The results were interpreted in the context of those expected from the largest published meta-analysis of cohort studies, totalling 958 000 people.

PARTICIPANTS

464 000 people defined into three mutually exclusive categories: participants with no history of vascular disease, a history of CHD, or a history of stroke.

RESULTS

In the blood pressure difference trials beta blockers had a special effect over and above that due to blood pressure reduction in preventing recurrent CHD events in people with a history of CHD: risk reduction 29% (95% confidence interval 22% to 34%) compared with 15% (11% to 19%) in trials of other drugs. The extra effect was limited to a few years after myocardial infarction, with a risk reduction of 31% compared with 13% in people with CHD with no recent infarct (P=0.04). In the other blood pressure difference trials (excluding CHD events in trials of beta blockers in people with CHD), there was a 22% reduction in CHD events (17% to 27%) and a 41% (33% to 48%) reduction in stroke for a blood pressure reduction of 10 mm Hg systolic or 5 mm Hg diastolic, similar to the reductions of 25% (CHD) and 36% (stroke) expected for the same difference in blood pressure from the cohort study meta-analysis, indicating that the benefit is explained by blood pressure reduction itself. The five main classes of blood pressure lowering drugs (thiazides, beta blockers, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and calcium channel blockers) were similarly effective (within a few percentage points) in preventing CHD events and strokes, with the exception that calcium channel blockers had a greater preventive effect on stroke (relative risk 0.92, 95% confidence interval 0.85 to 0.98). The percentage reductions in CHD events and stroke were similar in people with and without cardiovascular disease and regardless of blood pressure before treatment (down to 110 mm Hg systolic and 70 mm Hg diastolic). Combining our results with those from two other studies (the meta-analyses of blood pressure cohort studies and of trials determining the blood pressure lowering effects of drugs according to dose) showed that in people aged 60-69 with a diastolic blood pressure before treatment of 90 mm Hg, three drugs at half standard dose in combination reduced the risk of CHD by an estimated 46% and of stroke by 62%; one drug at standard dose had about half this effect. The present meta-analysis also showed that drugs other than calcium channel blockers (with the exception of non-cardioselective beta blockers) reduced the incidence of heart failure by 24% (19% to 28%) and calcium channel blockers by 19% (6% to 31%).

CONCLUSIONS

With the exception of the extra protective effect of beta blockers given shortly after a myocardial infarction and the minor additional effect of calcium channel blockers in preventing stroke, all the classes of blood pressure lowering drugs have a similar effect in reducing CHD events and stroke for a given reduction in blood pressure so excluding material pleiotropic effects. The proportional reduction in cardiovascular disease events was the same or similar regardless of pretreatment blood pressure and the presence or absence of existing cardiovascular disease. Guidelines on the use of blood pressure lowering drugs can be simplified so that drugs are offered to people with all levels of blood pressure. Our results indicate the importance of lowering blood pressure in everyone over a certain age, rather than measuring it in everyone and treating it in some.

Ascertainment and accuracy of Down syndrome cases reported in congenital anomaly registers in England and Wales

OBJECTIVE

Congenital anomaly registers allow the rates of anomalies to be monitored and are essential for understanding their epidemiology. We estimate the ascertainment and accuracy of records of Down syndrome (DS) on national and regional registers in England and Wales.

METHODS

Probabilistic record linkage was used to match records of DS from three sources: the National Down Syndrome Cytogenetic Register (NDSCR), seven regional members of the British Isles Network of Congenital Anomaly Registers (BINOCAR) and the National Congenital Anomaly System (NCAS). Capture-recapture methods were then used to estimate the ascertainment of each register.

RESULTS

The NDSCR and BINOCAR registers ascertain around 95% of both pre-natally and post-natally diagnosed cases of DS. NCAS collects data only on births and ascertains 55% of cases of DS births, which is currently around 25% of all DS diagnoses. NCAS ascertainment varies according to whether a BINOCAR register covering the same area contributes information to NCAS, varying from 80% in areas where regional registers contribute to 50% where regional registers do not.

CONCLUSIONS

Active case finding through regional registers is essential for monitoring congenital anomalies. The ascertainment of the NDSCR and BINOCAR is sufficient to provide reliable epidemiology and surveillance of congenital anomalies, whereas that of NCAS is not.

Multiple-marker screening for Down's syndrome: a method of assessing the statistical robustness of proposed tests

OBJECTIVES

Antenatal screening for Down's syndrome relies on the use of multiple markers in combination. Markers that are highly correlated can cause statistical instability. We used the maximum variance inflation factor (VIF(max)) to determine whether a screening test using multiple markers was robust to imprecision in the estimation of the marker distribution parameters.

METHODS

The VIF(max) for a specified screening test was calculated from the correlations between markers in Down's syndrome pregnancies for six tests: integrated and serum integrated tests without repeat measurements, both tests with repeat measurements across trimesters analysed in the standard way, and both tests with repeat measurements analysed as cross-trimester (CT) marker ratios. The screening performance of each test using published parameter values, in terms of the false-negative rates for a 3% false-positive rate (FN(3)), were calculated for simulated populations with medians 0.2 standard deviations (SD) higher or lower than the published values (to reflect imprecision in parameter estimation) for pregnancy-associated plasma protein A and unconjugated oestriol in affected pregnancies. For each test, the VIF(max) value was compared with the coefficient of variation of the FN(3) (FN(3) CV). An independent set of 27 Down's syndrome pregnancies was used to determine how many had meaningless low risks (<1 in 10,000) with each test.

RESULTS

Tests with VIF(max) values greater than 5 had FN(3)CV values over 50%, but those with VIF(max) values less than 5 had FN(3) CV values less than 21%. The numbers of Down's syndrome pregnancies with meaningless low risk estimates in the independent set were 18 (64%) in tests with VIF(max) values > or =5 and none for those with values <5.

CONCLUSION

VIF(max) values of 5 or more suggest instability. The tests using CT marker ratios were stable (VIF(max) < 3), but the tests using repeat measurements in the standard manner were not (VIF(max) > 5).

Measures of striatal insulin resistance in a 6-hydroxydopamine model of Parkinson's disease

Clinical evidence has shown a correlation between Parkinson's disease (PD) and Type 2 Diabetes (T2D), as abnormal glucose tolerance has been reported in >50% of PD patients. The development of insulin resistance and the degeneration of nigrostriatal dopamine (DA) neurons are both mediated by oxidative mechanisms, and oxidative stress is likely a mechanistic link between these pathologies. Although glucose uptake in neuronal tissues is primarily non-insulin dependent, proteins involved in insulin signaling, such as insulin receptor substrate 2 (IRS2) and glucose transporter 4 (GLUT4), are present in the basal ganglia. The purpose of this study was to determine whether nigrostriatal DA depletion affects measures of insulin resistance in the striatum. Six weeks after 6-hydroxydopamine (6-OHDA) infusion into the medial forebrain bundle, rats were classified as having either partial (20-65%) or severe (90-99%) striatal DA depletion. Increased IRS2 serine phosphorylation, a marker of insulin resistance, was observed in the DA-depleted striatum. Additionally, severe depletion resulted in decreased total IRS2, indicating possible degradation of the protein. Decreased phosphorylation of AKT and expression of the kinase glycogen synthase kinase-3 alpha (GSK3-alpha) was also measured in the striatum of severely DA-depleted animals. Finally, expression of heat shock protein 25 (Hsp25), which is protective against oxidative damage and can decrease stress kinase activity, was decreased in the striatum of lesioned rats. Together, these results support the hypothesis that nigrostriatal DA depletion impairs insulin signaling in the basal ganglia.

Lessons from an evaluation of a boater outreach program for manatee protection

Watercraft collisions account for 25-30% of manatee deaths annually in Florida. Education and outreach interventions for boaters are strategies for reducing manatee mortality. We evaluated the effectiveness of the Manatee Watch program by surveying primary boat users whose boats were approached by Manatee Watch. We compared the attitudes, knowledge, and behavioral intentions of boaters who received Manatee Watch materials with a control group of boaters observed by the Florida Marine Research Institute in Tampa Bay during 1999-2001. Results of the 51-item telephone survey with 499 boaters indicated that the Manatee Watch intervention had little effect on boater's attitudes, knowledge, and behaviors regarding manatees. However, individual attitude scores were positively correlated with safe boating behaviors in shallow waters including maintaining a slower speed and watching out for manatees. Overall knowledge about manatees was correlated with one manatee-safe boating behavior. To improve efficacy, educators should (a) incorporate evaluation into the planning stages of program development; (b) target messages to influence boaters' attitudes toward manatees and ecosystem health, and their feelings of ownership and empowerment; (c) facilitate active participation of the boaters; and (d) increase the duration and variety of intervention.

Wnt signaling promotes hematoendothelial cell development from human embryonic stem cells

Human embryonic stem cells (hESCs) provide an important means to effectively study soluble and cell-bound mediators that regulate development of early blood and endothelial cells in a human model system. Here, several complementary methods are used to demonstrate canonical Wnt signaling is important for development of hESC-derived cells with both hematopoietic and endothelial potential. Analyses using both standard flow cy-tometry, as well the more detailed high-throughput image scanning flow cytometry, characterizes sequential development of distinct early developing CD34(bright)CD31(+)Flk1(+) cells and a later population of CD34(dim)CD45(+) cells. While the CD34(bright)CD31(+)Flk1(+) have a more complex morphology and can develop into both endothelial cells and hematopoietic cells, the CD34(dim)CD45(+) cells have a simpler morphology and give rise to only hematopoietic cells. Treatment with dickkopf1 to inhibit Wnt signaling results in a dramatic decrease in development of cells with hematoendothelial potential. In addition, activation of the canonical Wnt signaling pathway in hESCs by coculture with stromal cells that express Wnt1, but not use of noncanonical Wnt5-expressing stromal cells, results in an accelerated differentiation and higher percentage of CD34(bright)CD31(+)Flk1(+) cells at earlier stages of differentiation. These studies effectively demonstrate the importance of canonical Wnt signaling to mediate development of early hematoendothelial progenitors during human development.

Efficient and stable transgene expression in human embryonic stem cells using transposon-mediated gene transfer

Efficient and stable genetic modification of human embryonic stem (ES) cells is required to realize the full scientific and potential therapeutic use of these cells. Currently, only limited success toward this goal has been achieved without using a viral vector. The Sleeping Beauty (SB) transposon system mediates nonviral gene insertion and stable expression in target cells and tissues. Here, we demonstrate use of the nonviral SB transposon system to effectively mediate stable gene transfer in human ES cells. Transposons encoding (a) green fluorescent protein coupled to the zeocin gene or (b) the firefly luciferase (luc) gene were effectively delivered to undifferentiated human ES cells with either a DNA or RNA source of transposase. Only human ES cells cotransfected with transposon- and transposase-encoding sequences exhibited transgene expression after 1 week in culture. Molecular analysis of transposon integrants indicated that 98% of stable gene transfer resulted from transposition. Stable luc expression was observed up to 5 months in human ES cells cotransfected with a transposon along with either DNA or RNA encoding SB transposase. Genetically engineered human ES cells demonstrated the ability to differentiate into teratomas in vivo and mature hematopoietic cells in vitro while maintaining stable transgene expression. We conclude that the SB transposon system provides an effective approach with several advantages for genetic manipulation and durable gene expression in human ES cells.

The proportions of Down's syndrome pregnancies detected prenatally in England and Wales from 1989 to 2004

OBJECTIVES

The proportion of Down's syndrome pregnancies detected prenatally in England and Wales is lower in younger mothers than in older mothers. This paper examines the reasons for this apparent age inequality.

METHODS

We used data from the National Down Syndrome Cytogenetic Register (NDSCR) to examine the time trend of the proportion of Down's syndrome pregnancies diagnosed prenatally according to maternal age over the years 1989-2004 in England and Wales.

RESULTS

A lower proportion of younger mothers had their Down's syndrome pregnancy detected prenatally than older mothers; however, this gap has been closing over time. For example, for mothers under 25 years of age only 13% of Down's syndrome pregnancies were detected prenatally from 1989 to 1992, with this figure rising to 34% in 2001-2004, compared with proportions of 74% in both periods for mothers over 44 years of age. A lower uptake of screening among younger women could not explain these differences. The differences in detection rates of the screening methods according to maternal age, particularly of the older screening tests, could account for these differences.

CONCLUSIONS

The closing gap between the proportions of younger and older women having their affected pregnancy prenatally diagnosed is a confirmation of the improvement of screening methods over time.

Insulin-like growth factors and cancer: no role in screening. Evidence from the BUPA study and meta-analysis of prospective epidemiological studies

Insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), and insulin-like growth factor binding protein-3 (IGFBP-3) were measured in frozen serum samples from 1051 men with cancer and 3142 controls in a nested case-control study from the British United Provident Association (BUPA) study cohort and associations with 14 cancers were examined, including prostate, colorectal, and lung. A meta-analysis of studies on these three cancer sites was also conducted. In the meta-analysis the odds ratio between the highest quartile IGF-1 group and the lowest quartile group was 1.31 (95% confidence interval (CI): 1.03-1.67) for prostate, 1.37 (1.05-1.78) for colorectal and 1.02 (0.80-1.31) for lung cancer, and for IGF-2 it was 0.72 (0.36-1.44) for prostate and 1.95 (1.26-3.00) for colorectal cancer. Results from the BUPA study were consistent with the estimates from the other studies. There were no statistically significant associations with IGFBP-3 and any of the cancer sites considered. Our results suggest that IGF-1, IGF-2, and IGFBP-3 measurements have no value in cancer screening, although IGF-1 and IGF-2 may be of aetiological significance in relation to colorectal and prostate cancer.

Understanding barriers to implementation of an adaptive land management program

The Florida Fish and Wildlife Conservation Commission manages over 650,000 ha, including 26 wildlife management and environmental areas. To improve management, they developed an objective-based vegetation management (OBVM) process that focuses on desired conditions of plant communities through an adaptive management framework. Our goals were to understand potential barriers to implementing OBVM and to recommend strategies to overcome barriers. A literature review identified 47 potential barriers in six categories to implementation of adaptive and ecosystem management: logistical, communication, attitudinal, institutional, conceptual, and educational. We explored these barriers through a bureau-wide survey of 90 staff involved in OBVM and personal interviews with area managers, scientists, and administrators. The survey incorporated an organizational culture assessment instrument to gauge how institutional factors might influence OBVM implementation. The survey response rate was 69%. Logistics and communications were the greatest barriers to implementing OBVM. Respondents perceived that the agency had inadequate resources for implementing OBVM and provided inadequate information. About one-third of the respondents believed OBVM would decrease their job flexibility and perceived greater institutional barriers to the approach. The 43% of respondents who believed they would have more responsibility under OBVM also had greater attitudinal barriers. A similar percentage of respondents reported OBVM would not give enough priority to wildlife. Staff believed that current agency culture was hierarchical but preferred a culture that would provide more flexibility for adaptive management and would foster learning from land management activities. In light of the barriers to OBVM, we recommend the following: (1) mitigation of logistical barriers by addressing real and perceived constraints of staff, funds, and other resources in a participatory manner; (2) mitigation of communication barriers through interpersonal and electronic communication channels; (3) development of an OBVM external advisory committee; and (4) adoption of characteristics of an organizational culture that promotes flexibility and learning.

Hematopoietic engraftment of human embryonic stem cell-derived cells is regulated by recipient innate immunity

Human embryonic stem cells (hESCs) provide an important means to characterize early stages of hematopoietic development. However, the in vivo potential of hESC-derived hematopoietic cells has not been well defined. We demonstrate that hESC-derived cells are capable of long-term hematopoietic engraftment when transplanted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Human CD45(+) and CD34(+) cells are identified in the mouse bone marrow (BM) more than 3 months after injection of hESCs that were allowed to differentiate on S17 stromal cells for 7-24 days. Secondary engraftment studies further confirm long-term repopulating cells derived from hESCs. We also evaluated two mechanisms that may inhibit engraftment: host immunity and requirement for homing to BM. Treatment with anti-ASGM1 antiserum that primarily acts by depletion of natural killer cells in transplanted mice leads to improved engraftment, likely due to low levels of HLA class I expressed on hESCs and CD34(+) cells derived from hESCs. Intra-BM injection also provided stable engraftment, with hematopoietic cells identified in both the injected and contra-lateral femur. Importantly, no teratomas are evident in animals injected with differentiated hESCs. These results demonstrate that SCID-repopulating cells, a close surrogate for hematopoietic stem cells, can be derived from hESCs. Moreover, both adaptive and innate immune effector cells may be barriers to engraftment of these cells.

Recurrences of free trisomy 21: analysis of data from the National Down Syndrome Cytogenetic Register

OBJECTIVES

To determine the recurrence risk of a free trisomy 21 pregnancy.

METHODS

Data from the National Down Syndrome Cytogenetic Register (NDSCR), which contains information on nearly all cases of Down syndrome between 1989 and 2001 in England and Wales were used. Among 11 281 women with a Down syndrome pregnancy who had had at least one previous pregnancy there were 95 women who had had a previous Down syndrome pregnancy.

RESULTS

Women who have had a previous Down syndrome pregnancy have a constant absolute excess risk above their maternal age-related risk of having a subsequent affected pregnancy. This absolute excess risk is determined by the age at which the affected pregnancy occurred and is higher for younger than for older women. For example, after a Down syndrome pregnancy at age 20, this excess is 0.62% (95% CI: 0.24 to 1.15%) at early second trimester, and, after one at age 40, it is 0.04% (95% CI: 0.01 to 0.07%).

CONCLUSION

More precise risk estimates by single year of maternal age for use in genetic counselling are provided, but they need validation from other studies before they are incorporated in the risk estimation routines used in Down syndrome screening programmes.

Risk of a Down syndrome live birth in women 45 years of age and older

OBJECTIVES

To determine the risk of a Down syndrome (DS) live birth for women 45 years of age and over.

METHODS

A meta-analysis of data from five published articles, 13 EUROCAT congenital anomaly population registers and two unpublished sources.

RESULTS

Information was available on the number of DS live births occurring amongst 13,745 live births to women 45 years of age and over. Information was also available on DS pregnancies diagnosed prenatally that were subsequently terminated. These pregnancies were adjusted for expected fetal loss to estimate the number of live births that would have occurred in the absence of prenatal diagnoses, when a total of 471 DS live births were estimated to have occurred. The risk of a DS birth did not increase for women 45 years of age and over. The average risk was 34 per 1000 births (95% CI: 31-37).

CONCLUSION

The risk of a DS live birth for women 45 years of age and over is considerably lower than has often been previously assumed. The most likely explanation is that women of this age are more likely to miscarry DS pregnancies than younger mothers.

Cytokine requirements differ for stroma and embryoid body-mediated hematopoiesis from human embryonic stem cells

OBJECTIVE

Human embryonic stem (ES) cells can be induced to differentiate into hematopoietic lineages either by stromal cell coculture or by formation of embryoid bodies (EBs). Here, we better characterize cell-bound and secreted factors that support this hematopoietic development.

METHODS

Human ES cells either cocultured on the mouse bone marrow cell line S17, or allowed to form EBs, were induced to differentiate in the presence of serum, serum-free conditions, and serum-free media supplemented with defined cytokines. To better characterize the requirement for stromal cell-bound or secreted proteins, S17 conditioned media and transwell cultures were also utilized.

RESULTS

In both models, CD34(+), CD45(+), and hematopoietic colony-forming cells (CFCs) were routinely derived. While hematopoietic development was diminished without serum, here we demonstrate with the stromal cell coculture model that addition of the growth factors stem cell factor (SCF), thrombopoietin (TPO), and Flt-3 ligand (Flt3L) to serum-free media does allow isolation of hematopoietic progenitors. However, these same three growth factors added to serum-free media do not support significant hematopoiesis in the EB system. However, addition of the mesoderm-inducing factors bone morphogenic protein-4 and vascular endothelial growth factor to EBs grown in serum-free media plus SCF, TPO, and Flt-3L does improve hematopoietic development.

CONCLUSION

These results demonstrate the utility of human ES cell to evaluate specific stimuli that regulate cell fate decisions and the survival of specific lineages. Moreover, the method used to promote differentiation of ES cells may alter the cytokines or growth factors required to isolate specific cell types.

Is cascade testing a sensible method of screening a population for autosomal recessive disorders?

Our aim was to evaluate "cascade testing" as a method of screening a population for autosomal recessive disorders. We used computer simulations to estimate screening performance according to carrier frequency, whether testing would extend to siblings, first or second cousins of identified carriers and family size. Cascade testing in populations with the distribution of family size current in England and Wales would require locating and testing a small proportion of the population as expected, but would detect few cases. For cystic fibrosis (carrier frequency of 4%), testing all siblings and first cousins of all identified carriers would require locating and testing only 1.9% of the whole population, but would detect only 15% of all new cases. Similarly for congenital adrenal hyperplasia (carrier frequency of 1%), testing all siblings and first cousins of all identified carriers would require locating and testing only 0.1% of the whole population, but would detect only 3.1% of all new cases. The detection rate increases with increasing carrier frequency, family size and extending the testing to second cousins of identified carriers, but at the cost of greater increases in the proportion of the population located and tested. The performance of cascade testing is too poor to justify its introduction into practice as a screening test for any autosomal recessive disorder.

Family or friends: who plays a greater supportive role for Latino college students?

This study compared the relative contribution of perceived family and friend support to psychological well-being and distress and examined whether family or friend support moderated the effects of stress on psychological adjustment in 338 Latino (228 Mexican American, 110 Central American) college students from a predominantly Latino university. Two multiple regressions, controlling for gender, socioeconomic level, acculturation level, and stresses (generic college, acculturative, and minority status), showed that friend support made a slightly greater contribution to well-being than family support, and friend support and not family support protected against psychological distress. Neither family nor friend support moderated the effects of stress on psychological adjustment. Further examination of these variables that assess common-specific stresses within a culture-specific theoretical framework is recommended.

Value of low dose combination treatment with blood pressure lowering drugs: analysis of 354 randomised trials

OBJECTIVE

To determine the average reduction in blood pressure, prevalence of adverse effects, and reduction in risk of stroke and ischaemic heart disease events produced by the five main categories of blood pressure lowering drugs according to dose, singly and in combination.

DESIGN

Meta-analysis of 354 randomised double blind placebo controlled trials of thiazides, beta blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, and calcium channel blockers in fixed dose.

SUBJECTS

40,000 treated patients and 16,000 patients given placebo.

MAIN OUTCOME MEASURES

Placebo adjusted reductions in systolic and diastolic blood pressure and prevalence of adverse effects, according to dose expressed as a multiple of the standard (recommended) doses of the drugs.

RESULTS

All five categories of drug produced similar reductions in blood pressure. The average reduction was 9.1 mm Hg systolic and 5.5 mm Hg diastolic at standard dose and 7.1 mm Hg systolic and 4.4 mm Hg diastolic (20% lower) at half standard dose. The drugs reduced blood pressure from all pretreatment levels, more so from higher levels; for a 10 mm Hg higher blood pressure the reduction was 1.0 mm Hg systolic and 1.1 mm Hg diastolic greater. The blood pressure lowering effects of different categories of drugs were additive. Symptoms attributable to thiazides, beta blockers, and calcium channel blockers were strongly dose related; symptoms caused by ACE inhibitors (mainly cough) were not dose related. Angiotensin II receptor antagonists caused no excess of symptoms. The prevalence of symptoms with two drugs in combination was less than additive. Adverse metabolic effects (such as changes in cholesterol or potassium) were negligible at half standard dose.

CONCLUSIONS

Combination low dose drug treatment increases efficacy and reduces adverse effects. From the average blood pressure in people who have strokes (150/90 mm Hg) three drugs at half standard dose are estimated to lower blood pressure by 20 mm Hg systolic and 11 mm Hg diastolic and thereby reduce the risk of stroke by 63% and ischaemic heart disease events by 46% at age 60-69.

Cystic fibrosis: selecting the prenatal screening strategy of choice

Cystic fibrosis is a serious disorder. Research into the treatment of affected individuals is in progress, but a cure is not expected in the near future. In this review, we demonstrate that prenatal screening for cystic fibrosis meets the requirements for a worthwhile screening programme. We explain the reasons that have led us to conclude that one approach ('couple screening') is the method of choice. The couple-based approach calls for reporting results to the couple as a unit. Only if both parents are found to be carriers is the result designated screen-positive and an amniocentesis or chorionic villus sampling offered. This offers a substantial reduction in the proportion of women with unaffected pregnancies with positive results (the false-positive rate) compared with other methods without reducing the detection of affected pregnancies. It also avoids creating a screen-positive group for which no definitive diagnosis is available. This is a problem with other screening methods. The couple method can achieve a 72% detection rate for a 0.1% false-positive rate. The screening method is simple, non-invasive, reliable, safe and reasonably cost effective. Existing programmes have shown that screening using this method is acceptable to health care professionals and patients. Setting up a national prenatal screening programme for cystic fibrosis is timely and should be implemented using the couple screening method.

A new approach to antenatal screening for Fragile X syndrome

OBJECTIVES

To describe a new approach to antenatal screening for Fragile X syndrome and to evaluate its effectiveness.

METHODS

We propose that Fragile X syndrome should be considered as a different disorder in males and in females. We also propose that only male Fragile X syndrome should be screened for, so the initial screening test would be the determination of fetal sex. This can now be performed from eight-weeks gestation using a polymerase chain reaction (PCR) analysis on maternal serum. If this test reveals a male fetus, then the same blood sample can be used to determine the CGG repeat length in the DNA of the mother, again using the PCR technique and a Southern blot analysis where necessary. Mothers with positive results (>58 repeats) would be offered antenatal diagnosis (chorionic villus sampling or amniocentesis) to determine the CGG repeat length in cells from the fetus. The screening performance of this strategy was determined using the performance of the component tests.

RESULTS

The proposed strategy for screening for male Fragile X syndrome would have a 99% detection rate and a 0.1% false-positive rate.

CONCLUSION

After antenatal screening for Down syndrome, the proposed screening strategy would be the most effective method of preventing the birth of males with severe mental retardation. It would have a higher detection rate and a lower false-positive rate than any other antenatal screening programme currently being undertaken, and there would be virtually no prenatal diagnosis of female Fragile X syndrome, which, because such a high proportion are phenotypically normal, has been a barrier to the introduction of screening.

Comparison of models of maternal age-specific risk for Down syndrome live births

OBJECTIVES

To display and compare the different published formulae that specify the association between maternal age and the risk of a Down syndrome live birth.

METHODS

Papers published since 1987 on the prevalence of Down syndrome live births in relation to maternal age were located using MEDLINE and the references given in other papers. The data series and the models fitted to them were plotted to obtain a visual idea of their similarities and differences.

RESULTS

The observed and modelled age-specific rates for Down syndrome births were remarkably similar in all published series of data for women up to the age of 35, were reasonably similar for women aged 35 to 45, but differed for women older than 45.

CONCLUSION

In practice, the overall small differences in age-related risk between the different studies did not materially affect the performance of antenatal screening for Down syndrome. If a choice is to be made, the analysis based on the National Down Syndrome Cytogenetic Register (NDSCR) has marginal advantages since it is based on the largest data set and the corresponding model fits the data well. More data is needed to clarify the pattern of risk with maternal age among women over 45 years of age.

Revised estimates of the maternal age specific live birth prevalence of Down's syndrome

OBJECTIVES

To revise the estimates of maternal age specific live birth prevalence of Down's syndrome in the absence of antenatal screening and selective termination using newly available data.

SETTING AND DESIGN

Data were used from the National Down Syndrome Cytogenetic Register (NDSCR), which contains information on nearly all antenatally or postnatally diagnosed cases of Down's syndrome in which a karyotype was confirmed between 1989 and 1998 in England and Wales. It is the largest single series of data on the prevalence of Down's syndrome.

RESULTS AND CONCLUSION

The prevalence does not continue increasing at an increasing rate with age above age 45 as has been previously assumed. Above this age the rate of increase declines with increasing age. The overall age pattern is sigmoidal. A new logit logistic model is proposed which fits the data well. The risk of a Down's syndrome live birth is given by: risk=1/(1+exp(7.330-4.211/(1+exp(-0.282x(age-37.23))))).

Dopaminergic and serotonergic activities of imidazoquinolinones and related compounds

The synthesis of 5-(dipropylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij] quinolin-2(1H)-one (5), a potent dopamine D2 agonist showing high dopamine/serotonin (5HT1A) selectivity, is described. Dopaminergic activity is associated with the (R)-enantiomer of 5; the (S)-enantiomer shows no dopaminergic activity. A series of analogues where the imidazolone ring was modified to various 5- or 6-membered heterocyclic rings were prepared. Some of these compounds showed a combination of dopaminergic and serotonergic activity, while one compound, 6-(dipropylamino)-1,2,6,7-tetrahydro-3H,5H-pyrido[3,2,1- ij]quinazolin-3-one (24), was a selective serotonergic agonist. Various analogues of 5 where the dipropylamine substituent was modified were prepared. Most of these showed reduced dopaminergic activity, while several were as potent as 5 at the serotonin 5HT1A receptor. Orientations for the new compounds at dopamine and serotonin receptors are proposed and compared with those of other tricyclic ligands known to have high affinity at these receptors.

Multiple marker second trimester serum screening for pre-eclampsia

OBJECTIVE

To investigate whether an appropriate combination of maternal serum inhibin A, free beta-human chorionic gonadotropin (free beta-hCG), unconjugated estriol (uE3), and alpha-fetoprotein (AFP) may be an effective means of screening for pre-eclampsia in the second trimester of pregnancy.

SETTING

Women who attended an antenatal clinic in Oxford, from whom serum samples were stored, 19 of whom subsequently developed pre-eclampsia.

METHODS

Serum inhibin A, free beta-hCG, uE3, and AFP were measured in 32 serum samples collected from the 19 women who developed pre-eclampsia and, for each sample, in three control samples collected from women with unaffected pregnancies matched for gestational age and maternal age.

RESULTS

In pregnancies that developed pre-eclampsia the median inhibin A value was raised (1.7 multiples of the median (MoM) for unaffected pregnancies (95% confidence interval (95% CI) 1.1 to 2.7 MoM), the median free beta-hCG was raised (2.1, 1.4 to 3.3 MoM) and the median uE3 was lowered (0.8, 0.6 to 0.98 MoM) after 19 completed weeks of gestation and at least 2 weeks before the onset ofproteinuria. Values of AFP were similar in affected and unaffected pregnancies. Combining the values ofinhibin A, free beta-hCG, and uE3 to form a screening test would detect an estimated 55% of affected pregnancies with a false positive rate of 5%.

CONCLUSIONS

Inhibin A, free beta-hCG, and uE3 in combination may be a useful screening test during the second trimester for pre-eclampsia.

Quantifying the effect of folic acid

BACKGROUND

Folic acid is known to prevent neural-tube defects (NTDs) but the size of the effect for a given dose is unclear. We aimed to quantify such an effect.

METHODS

We used published data from 13 studies of folic acid supplementation on serum folate concentrations and results from a large cohort study of the risk of NTDs according to serum folate, to measure the preventive effect of specified increases in intake of folic acid.

FINDINGS

Serum folate concentrations increase by 0.94 ng/mL (95% CI 0.77-1.10) for every 0.1 mg/day increase in folic acid intake in women aged 20-35 years, and about double that in people aged 40-65. Every doubling of serum folate concentration roughly halves the risk of an NTD. These two effects can be combined to predict the reduction in risk according to intake of extra folic acid and background serum folate concentration. Such results predict that the preventive effect is greater in women with low serum folate than in those with higher concentrations. The results have also been used to predict direct observations from large randomised trials and the effect of food fortification. From a typical western background serum folate of 5 ng/mL, about 0.2 mg/day (the US level of folic acid fortification) would be expected to reduce NTDs by about 20%; a similar effect can be expected from the current British recommendation (0.24 mg/day). An increase of 0.4 mg/day would reduce risk by about 36%, of 1 mg/day by 57%, and taking a 5-mg tablet daily would reduce risk by about 85%.

INTERPRETATION

Folic acid fortification levels should be increased. Additionally women planning a pregnancy should take 5 mg folic acid tablets daily, instead of the 0.4 mg dose presently recommended.