Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10-14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log10 SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free beta-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free beta-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21.

Comparison of MPEG-1 digital videotape with digitized sVHS videotape for quantitative echocardiographic measurements

Digital format is rapidly emerging as a preferred method for displaying and retrieving echocardiographic studies. The qualitative diagnostic accuracy of Moving Pictures Experts Group (MPEG-1) compressed digital echocardiographic studies has been previously reported. The goals of the present study were to compare quantitative measurements derived from MPEG-1 recordings with the super-VHS (sVHS) videotape clinical standard. Six reviewers performed blinded measurements from still-frame images selected from 20 echocardiographic studies that were simultaneously acquired in sVHS and MPEG-1 formats. Measurements were obtainable in 1401 (95%) of 1486 MPEG-1 variables compared with 1356 (91%) of 1486 sVHS variables (P <.001). Excellent agreement existed between MPEG-1 and sVHS 2-dimensional linear measurements (r = 0.97; MPEG-1 = 0.95[sVHS] + 1.1 mm; P <.001; Delta = 9% +/- 10%), 2-dimensional area measurements (r = 0.89), color jet areas (r = 0.87, p <.001), and Doppler velocities (r = 0.92, p <.001). Interobserver variability was similar for both sVHS and MPEG-1 readings. Our results indicate that quantitative off-line measurements from MPEG-1 digitized echocardiographic studies are feasible and comparable to those obtained from sVHS.

Fetal heart rate in chromosomally abnormal fetuses

OBJECTIVES

To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation.

METHODS

Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome.

RESULTS

In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18.

CONCLUSIONS

Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.

Normal values of regional left ventricular endocardial motion: multicenter color kinesis study

Our goal was to establish normal values for quantitative color kinesis indexes of left ventricular (LV) wall motion over a wide range of ages, which are required for objective diagnosis of regional systolic and diastolic dysfunction. Color-encoded images were obtained in 194 normal subjects (95 males, 99 females, age 2 mo to 79 yr) in four standard views. Quantitative indexes of magnitude and timing of systolic and diastolic function were studied for age- and gender-related differences. Normal limits of all ejection and filling indexes were in a narrow range (< or =25% of the mean), with no major gender-related differences. Despite invariable ejection fractions, both peak filling and ejection rates decreased with age (30 and 20%, correspondingly) with a concomitant increase in mean filling and ejection times, resulting in five- and twofold increases in the late to early filling and ejection ratios, correspondingly. Diastolic asynchrony increased with age (from 4.7 +/- 2.0 to 6.4 +/- 3.2 from the 2nd to 7th decade). The normal values of color kinesis indexes should allow objective detection of regional LV systolic and diastolic dysfunction.

Stable lead isotope ratios from distinct anthropogenic sources in fish otoliths: a potential nursery ground stock marker

Variations measured in the lead (Pb) stable isotope ratios in otoliths of juvenile tropical reef fish Scarus perspiculatus, Abudefduf abdominalis and Dascyllus albisella reflect mixing of anthropogenic lead from the Kaneohe Bay watershed and 'background' lead characteristic of the adjacent ocean. The otoliths and water samples collected in a transect across the bay demonstrated nearly identical Pb isotopic trends. The Pb isotopic composition of the watershed has a low 206Pb/204Pb signature primarily reflecting past combustion of tetra-ethyl Pb additive in fuels. Ocean water not contaminated by this watershed signature has a different, high 206Pb/204Pb isotopic composition, similar to previously measured Asian anthropogenic aerosols and natural eolian dusts, where the anthropogenic signal dominates. Where a history of past anthropogenic Pb contamination exists, it may be possible to use the ratios of Pb stable isotopes in fish otoliths to reconstruct the nursery grounds of fish.

One stop clinic for assessment of risk for fetal anomalies: a report of the first year of prospective screening for chromosomal anomalies in the first trimester

OBJECTIVE

To evaluate the introduction of a one stop multidisciplinary clinic for screening for fetal chromosomal abnormalities in the first trimester by a combination of maternal serum biochemistry and ultrasonography providing a risk of chromosomal abnormalities within a one hour clinic visit.

DESIGN

One year retrospective review of screening performance.

POPULATION

All women attending for routine antenatal care. The population included 4,190 singleton pregnancies in women of all ages screened between 10 weeks and 3 days and 13 weeks and 6 days of gestation between the periods 1 June 1998 and 31 May 1999 in a district general hospital antenatal clinic.

METHODS

All women booked into the clinic were offered screening by a combination of maternal serum free beta human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein A (PAPP-A) and fetal nuchal translucency thickness. Women at increased risk of carrying a fetus with trisomy 21 or trisomy 18/13 (> or =1 in 300 at sampling) were offered counselling and an invasive diagnostic procedure. Follow up of the outcome of all pregnancies was carried out.

MAIN OUTCOME MEASURES

The detection rate for trisomy 21, trisomy 18/13 and all aneuploides, false positive rate, uptake of screening, uptake of chorionic villus sampling in women identified at increased risk and fetal loss after chorionic villus sampling.

RESULTS

Overall 97.6% of the women (4,088/4,190) accepted first trimester screening. The rate of detection of trisomy 21 was 86% (6/7), for trisomy 18/13 100% (9/9) and for all aneuploides 95% (18/19). Fetal death at presentation was found in 1.6% of pregnancies (69/4,088). Of women who accepted screening, 6.1% (257/4,088) presented too late for fetal nuchal translucency measurement and 6.5% of the women (271/4,088) presented too early. The false positive rate was 6.7% (253/3,762). Uptake of invasive testing was 83% (207/253).

CONCLUSION

First trimester prenatal screening for chromosomal abnormalities using a combination of maternal serum biochemistry and fetal nuchal translucency thickness can achieve detection rates in excess of 90%. These services can be provided in a one stop multidisciplinary clinic.

The influence of parity and gravidity on first trimester markers of chromosomal abnormality

We have studied changes in first trimester fetal nuchal translucency (NT) and maternal serum free beta-hCG and PAPP-A with gravidity and parity in 3252 singleton pregnancies unaffected by chromosomal abnormality or major pregnancy complications. We have shown that gravidity and parity is associated with a small but progressive decrease in fetal NT and a small but progressive increase in free beta-hCG and PAPP-A. None of these small changes with increasing gravidity or parity are statistically significant and hence correction for these variables is not necessary when considering first trimester screening for chromosomal abnormalities.

First trimester maternal serum free beta human chorionic gonadotrophin and pregnancy associated plasma protein A as predictors of pregnancy complications

OBJECTIVE

To examine the value of first trimester maternal serum free beta human chorionic gonadotrophin (beta hCG) and pregnancy associated plasma protein A (PAPP-A) as predictors of pregnancy complications.

DESIGN

Screening study.

SETTING

Antenatal clinics.

POPULATION

Singleton pregnancies at 10-14 weeks of gestation.

METHODS

Maternal serum free beta hCG and PAPP-A were measured at 10-14 weeks of gestation in 5,584 singleton pregnancies. In the 5,297 (94.9%) pregnancies with complete follow up free beta hCG and PAPP-A were compared between those with normal outcome and those resulting in miscarriage, spontaneous preterm delivery, pregnancy induced hypertension or fetal growth restriction and in those with pre-existing or gestational diabetes.

RESULTS

Maternal serum PAPP-A increased and beta hCG decreased with gestation. The multiple of median maternal serum PAPP-A was significantly lower in those pregnancies resulting in miscarriage, pregnancy induced hypertension, growth restriction and in those with pre-existing or gestational diabetes mellitus, but not in those complicated by spontaneous preterm delivery. The level was < 10th centile of the reference range in about 20% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 27% of those that developed gestational diabetes. Maternal serum free beta hCG was < 10th centile of the reference range in about 15% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 20% of those that developed gestational diabetes.

CONCLUSION

Low maternal serum PAPP-A or beta hCG at 10-14 weeks of gestation are associated with subsequent development of pregnancy complications.

Electronic transmission of digital echocardiographic studies: effects of MPEG compression

The acquisition, storage and retrieval of digital echocardiographic studies greatly facilitates image review and quantitation and permits the transmission of studies electronically. However, the considerable size of digital echocardiographic data files makes transmission over existing networks slow and impractical. Reduction in the size of these data files can be accomplished with digital image compression. We sought to evaluate the effects of MPEG-1 compression on the transfer time of digital echocardiographic studies over currently available network connections. Ninety consecutive routine clinical echocardiographic studies were randomly compressed at one of three compression ratios 60:1, 80:1, or 120:1 and sent to a receiving terminal using simulated transmission rates. Compression of digital echocardiographic studies at these ratios which, have been shown to maintain diagnostic image quality, reduced the size of digital echocardiographic studies to less than 1% of their original sizes which allowed transmission of echocardiographic studies over networks using 3ISDN or T1 lines with minimal waiting time.

The influence of fetal sex in screening for trisomy 21 by fetal nuchal translucency, maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In a study of 2923 normal pregnancies and 203 pregnancies affected by trisomy 21 we have shown a significant difference in the median MoM of the markers: fetal nuchal translucency, maternal serum free beta-hCG and PAPP-A in the presence of a female fetus compared with a male fetus. For maternal serum free beta-hCG levels are higher by 15% if the fetus is chromosomally normal and by 11% if the fetus has trisomy 21. For maternal serum PAPP-A the levels in chromosomally normal fetuses are 10% higher in the presence of a female fetus and 13% higher if the fetus has trisomy 21. In contrast, fetal nuchal translucency is 3-4% lower in both chromosomally normal and trisomy 21 female fetuses. The consequence of such changes when screening for trisomy 21 will be a reduction in the detection rate in female fetuses by a factor of 1-2%. Correction of risk algorithms for fetal sex, however, is probably not feasible, since ultrasound detection of fetal sex is only 70-90% accurate in the 10-14 week period.

The influence of fetal sex in screening for Down syndrome in the second trimester using AFP and free beta-hCG

In a study of 30 802 unaffected pregnancies and 90 cases of Down syndrome I have analysed second trimester maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG) and grouped the data by fetal sex. In pregnancies with an unaffected female fetus maternal serum AFP was significantly lower (3%) than in the presence of a male fetus, whilst free beta-hCG was significantly raised (7%) in the presence of a female fetus. These differences led to a significantly higher false positive rate in women carrying a female fetus (5.78% versus 4.64%). In pregnancies affected by Down syndrome the median AFP in the presence of a female fetus was not significantly different to that with a male fetus (0. 72 versus 0.73); similarly for free beta-hCG the difference (2.37 versus 2.48) was not statistically significant. Although the detection rate amongst male fetuses was slightly higher than in females (74% versus 66%), this was not statistically significant. Although fetal gender does appear to have a significant effect on maternal serum marker levels, leading to a higher false positive rate in females, in cases of Down syndrome there is no evidence that such marker differences are significant and consequently little evidence for any fetal gender bias in detection rates.

Second-trimester prenatal screening for Down syndrome and the relationship of maternal serum biochemical markers to pregnancy complications with adverse outcome

In a group of 26 524 control pregnancies and a group of 3728 pregnancies affected by one or more of the pregnancy complications of low birthweight, intra-uterine growth restriction (IUGR), preterm delivery and stillbirth, I have compared the relative risk of occurrence of these complications in pregnancies which had a raised maternal serum AFP (>2.0 MoM), raised maternal serum free beta-hCG (>2.0 MoM), low AFP (<0.5 MoM), low free beta-hCG (<0.5 MoM), combined raised AFP and free beta-hCG (>2.0 MoM), and in those with an increased Down syndrome risk (1 in 250 or greater). In the low birthweight group, only an increased AFP and decreased free beta-hCG showed significance with relative risks of 1.6 and 2.1. In the IUGR group, also only an increased AFP and decreased free beta-hCG showed significance with relative risks of 1.6 and 2.3. In the preterm delivery group, raised AFP, reduced free beta-hCG, and combined elevated AFP and free beta-hCG showed significance with relative risks of 3.8, 1.8 and 6.2. In the stillbirth group, raised AFP, reduced free beta-hCG, and combined elevated AFP and free beta-hCG showed significance with relative risks of 4.5, 2,4 and 7.2. An isolated raised free beta-hCG or an increased Down syndrome risk were not associated with an increased relative risk for any of the pregnancy complications investigated. However, apart from the six to seven-fold increased risk when both AFP and free beta-hCG are above 2.0 MoM, suggesting increased risk of preterm delivery or impending fetal death, the clinical utility of such significant differences is probably poor.

First trimester maternal serum AFP and total hCG in aneuploidies other than trisomy 21

Total human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) were measured in maternal serum at 10-14 weeks of gestation from 53 pregnancies affected by trisomy 18, 42 cases with trisomy 13, 46 with Turner's syndrome and 13 with other sex aneuploides. The only significant association was the finding of reduced levels of total hCG in cases of trisomy 18 and 13. The association of increased levels of AFP in cases of trisomy 18 with ventral wall defects and the slight increase in AFP in cases of sex chromosomal anomalies other than Turner's syndrome was found. AFP and total hCG are not likely to replace the markers free beta-hCG and PAPP-A in first trimester screening for chromosomal anomalies.

The influence of ethnic origin on first trimester biochemical markers of chromosomal abnormalities

In a first trimester study of 5422 Caucasian women, 752 Afro-Caribbean women and 170 Asian women we have shown that the median maternal serum marker MoMs for free beta-hCG and PAPP-A were 19% and 48% higher in Afro-Caribbean women and 19% higher and 35% higher in Asian women, compared to Caucasian women. Correcting for maternal weight made very little difference to the effect in Afro-Caribbeans (21% and 57% higher after weight correction) but reduced the effect in Asians (4% and 17% higher after weight correction ). It is estimated that correcting for maternal weight and ethnicity overall would increase the detection rate by a modest 1.4%. However, the effect on an individual's risk could result in as much as a two-fold increase in the patient specific risk for trisomy 21. The impact of ethnic origin seems to be greater than that observed with second trimester biochemical markers and larger studies are required in order to develop robust algorithms for correcting for ethnic origin in the first trimester.

Screening for triploidy by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In 25 cases of triploidy at 10-14 weeks of gestation, compared with 947 controls, the median multiple of the median (MoM) fetal nuchal translucency (NT) thickness was significantly increased (1.89 MoM), and maternal serum total and free beta-human chorionic gonadotrophin (hCG) were increased (3.13 MoM and 4.59 MoM respectively), alpha fetoprotein (AFP) was increased (2.14 MoM), and pregnancy associated plasma protein A (PAPP-A) was decreased (0.12 MoM). There are two types of triploidy. In type I, where the additional chromosome set is of paternal origin, the placenta is partially molar and the fetus is relatively well-grown. Type II, where the extra chromosome set is of maternal origin, is characterized by a small normal looking placenta and severe asymmetrical fetal growth restriction. In type I triploidy there was increased fetal NT (2.76 MoM), maternal serum total hCG (4.91 MoM), free beta-hCG (8.04 MoM), and AFP (3.22 MoM), and mildly decreased PAPP-A (0.75 MoM). In type II triploidy fetal NT was not increased (0.88 MoM), and there was a decrease in maternal serum total hCG (0.16 MoM), free beta-hCG (0.18 MoM), PAPP-A (0.06 MoM) and AFP (0.77 MoM). We conclude that a large proportion of triploidy cases of both phenotypes could be identified in the first trimester using NT, maternal serum free beta-hCG and PAPP-A with a combination of trisomy 21 risk and an atypicality approach.

Maternal serum free beta-hCG and PAPP-A in fetal sex chromosome defects in the first trimester

We have studied maternal serum free beta-hCG and PAPP-A, and fetal nuchal translucency (NT) in a series of 46 cases of fetal Turner's syndrome, 13 cases of other sex chromosomal anomalies and compared these with 947 control pregnancies in the first trimester. In cases of Turner's syndrome (45,X) the median fetal NT was significantly higher than in controls (4.76 MoM), the median PAPP-A was significantly lower (0.49 MoM), whilst the free beta-hCG was not significantly different (1.11 MoM). For NT, 93% (43/46) of cases were equal to or greater than the 95th centile of controls, for PAPP-A 35% (16/46) of cases were less than or equal to the 5th centile of controls and for free beta-hCG 15% (7/46) of cases were equal to or greater than the 95th centile of controls. For other sex chromosomal anomalies (47XXX, XXY, XYY) the median NT was increased (2.07 MoM) whilst PAPP-A was not significantly decreased (0.88 MoM) and free beta-hCG was not significantly different (1.07 MoM) from controls. Using a previously derived multivariate risk algorithm for trisomy 21, incorporating NT, PAPP-A, free beta-hCG and maternal age, 96% of the Turner's cases and 62% of the other sex chromosomal anomalies would have been identified.

Screening for trisomy 13 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In 42 cases of trisomy 13 at 10-14 weeks of gestation, compared with 947 controls, the median multiple of the median (MoM) of maternal serum free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy associated plasma protein A (PAPP-A) was significantly decreased (0.506 MoM and 0.248 MoM respectively), whilst fetal nuchal translucency was increased (2.872 MoM). In 38% and 71% of cases of trisomy 13 maternal serum free beta-hCG and PAPP-A was below the 5th centile of the appropriate normal range for gestation and in 62% of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, 90% of cases of trisomy 13 could be detected at a 0.5% false positive rate or 84% at a 0.1% false positive rate. We conclude that specific trisomy 13 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21 and trisomy 18.

Is English a dyslexic language?

McGuinness has suggested that there 'is no diagnosis and no evidence for any special type of reading disorder like dyslexia', and that poor teaching accounts for low levels of English literacy performance, rather than inherent personal deficits. Implicit in this is the assumption that some languages have simple grapheme-phoneme codes in which there is a one-to-one mapping, making them easy to teach and learn, while others have more complicated structures and are more difficult for teachers and students. There is now an increasing number of studies which demonstrate that readers in more transparent orthographies such as Italian, Spanish, Turkish, Greek and German have little difficulty in decoding written words, while English children have many more problems. Increasingly, lack of orthographic transparency in English is seen as having a powerful negative effect on the development of reading skills in English-speaking children. There is evidence that English-speaking children who fail to acquire reading skills may fall into two distinct categories: those who would succeed in languages, other than English, that have greater orthographic consistency; and those who would still have problems even with perfect orthographic transparency. The first, larger, group is let down by the interaction of poor teaching methods and an incomprehensible system of orthography. The present study examines word factors associated with poor spelling and reading that have been identified. Three factors account for the relative ease with which pupils can spell words: frequency of the word in the English language; length of the word; and the presence of 'tricky' letters or letter combinations. Data are presented illustrating the predictive model of spelling and reading which enables word difficulty to be calculated from the characteristics of English words. The implications the model has for teaching and learning English are elaborated, with reference to the possible benefits to be derived from mother-tongue teaching in British schools.

Is maternal serum total hCG a marker of trisomy 21 in the first trimester of pregnancy?

In a study of 130 first trimester cases of trisomy 21 and 959 controls we have shown that the median MoM for alpha-fetoprotein (AFP) is lower (0.82) and that for total human chorionic gonadotrophin (hCG) is higher (1.31) than in the control group. For AFP 15.3% of cases were below the 5th centile and for total hCG 19. 8% were above the 95th centile. The median shift observed for AFP and total hCG is poorer than that for pregnancy associated plasma protein-A (PAPP-A) or free beta-hCG and together with maternal age, AFP and total hCG could only be expected to detect 40% of cases. In combination with PAPP-A, total hCG would identify 52% of cases, somewhat less than the 67% observed with free beta-hCG and PAPP-A. However, we have demonstrated for total hCG a significant temporal change in median MoM with gestational age. Before 70 days the median MoM was less than 0.5, between 70 and 83 days this increased to 1.13, and between 84 and 97 days this increased to 1.52. This median shift has significant implications for interpreting previous studies and even more significant implications for detection rates. When population parameters specific to the gestational age in question are used, detection rates with total hCG and PAPP-A increase from 47% at 70-83 days to 60% at 84-97 days. This observation explains much of the confusion around total hCG in the first trimester and shows the importance of selecting analyte pairs and population parameters appropriate to the time in gestation when screening is performed.

Quantitative analysis of the developing rat kidney: absolute and relative volumes and growth curves

The development of the permanent kidney, or metanephros, is a complex process. In the present study, stereological methods were used at the light microscopic level to estimate the absolute volumes and volume densities of seven compartments in the developing rat metanephros, from embryonic day 14 (E14) to E21. Metanephroi from time-mated Sprague-Dawley rats were embedded whole in glycolmethacrylate, exhaustively sectioned at 2 microm and stained with PAS. The left metanephros from three embryos from each of three mothers were analysed at each of the ages (a total of 72 metanephroi). Relative volumes were multiplied by total metanephric volume to obtain absolute volumes. Total metanephric volume increased approximately 300-fold during the 7-day period studied. At E14, 92% of the metanephros was composed of undifferentiated mesenchyme, whilst the ureteric epithelium made up approximately 5% of the volume. By E21 the undifferentiated mesenchyme comprised 47% of the kidney, while the ureteric epithelium comprised 9% and the various components of developing nephrons (epithelial vesicles, comma-shaped bodies, S-shaped bodies, glomeruli, tubules) comprised 43%. Equations with prediction intervals describing the growth of the whole kidney as well as the absolute and relative growth of the seven kidney compartments were generated. These data provide a baseline for future studies on the roles of specific molecules in renal development.

Screening for trisomy 21 in twin pregnancies in the first trimester using free beta-hCG and PAPP-A, combined with fetal nuchal translucency thickness

In the first trimester of pregnancy the biochemical markers free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) are used for the prenatal screening of trisomy 21, either alone or in combination with nuchal translucency (NT) thickness. In this study, I have analysed the distribution of these biochemical markers in 159 twin pregnancies and compared this with 3466 singleton pregnancies. On average free beta-hCG values are 2.099 times greater in twins than in singletons and PAPP-A some 1.86 times greater. The width of the analyte distribution in twins is very similar to that in singleton pregnancies. Using statistical modelling techniques I have predicted that at a 5% false positive rate the detection rate in twins discordant for trisomy 21 will be 52% and in twins concordant for trisomy 21 will be 55%, if correction for twin pregnancy is carried out using the 'pseudo risk' approach. The detection rate using biochemical parameters is less than that achievable for twins using NT (75%). However, the combination of NT and maternal serum biochemistry will give detection rates approaching 80%. These rates are some 10% less than in singleton pregnancies, but nevertheless combining NT and biochemistry will allow high rates of detection of affected twins with the benefit of ultrasound and NT being able to specifically locate the affected twin. Twin screening using both modalities should be considered when introducing first trimester screening.

Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In a study of 50 cases of trisomy 18 compared with 947 controls we have found the median multiple of the median (MoM) of maternal serum free beta human chorionic gonadotrophin to be significantly decreased (0.281 MoM) in samples collected between the 10th and 14th week of gestation. Similarly, maternal serum pregnancy associated plasma protein A (PAPP-A) levels are also decreased (0.177 MoM), whilst the median nuchal translucency is significantly higher (3.272 MoM). Free beta-hCG MoM was less than the 5th centile of normal in 64 per cent of cases of trisomy 18 and for PAPP-A was less than the 5th centile in 78 per cent of cases. Also, in 78 per cent of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, we predict that 89 per cent of cases of trisomy 18 could be detected at a 1 per cent false-positive rate. We conclude that specific trisomy 18 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21.

Effects of MPEG compression on the quality and diagnostic accuracy of digital echocardiography studies

The advantages of digital echocardiography studies include ease of retrieval, review, comparison, duplication, and quantitation as well as the potential for moving studies over networks. However, the large amounts of data associated with digital echocardiography studies have posed new problems. Reduction of the amount of data can be accomplished with image compression, in particular MPEG-1 (Moving Pictures Expert Group), which is designed for dynamic image sequences. However the effects of different levels of compression on the quality and diagnostic content of echocardiographic images need to be established. Digital sequences of single cardiac cycles were acquired in 40 consecutive patients, MPEG-1-compressed at different effective ratios (60:1, 80:1, 120:1, 200:1, 300:1, 370:1, 500:1), reviewed, and scored for endocardial visualization. The overall visualization scores and percentages of nonvisualized segments in the compressed images were not different from the uncompressed images up to a compression ratio of 200:1. Differential effects of compression were noted on a segmental basis and also varied with baseline image quality. The ability to correctly identify regional wall motion abnormalities did not decrease until compression ratios of 1:200 or higher were used. Digital echocardiography loops, MPEG-1-compressed at an effective ratio of 200:1, demonstrate no degradation in endocardial visualization quality or diagnostic content. Compression at this ratio has the potential to reduce the storage size of digital echocardiography studies to less than 1% of their current size.

Second trimester levels of pregnancy associated plasma protein-A in cases of trisomy 18

In a study of 70 cases of trisomy 18 and 450 matched controls in the second trimester we have measured the maternal serum levels of the analytes alpha feto protein (AFP), free beta-human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein-A (PAPP-A). We have found the median multiple of the median (MoM) of maternal serum free beta-hCG to be significantly lower (0.327) than normal, as was the level of AFP (0.600). Levels of PAPP-A were reduced even further (0.108). Of the markers associated with trisomy 18 at this time PAPP-A was the most discriminatory, being lower than the 5 per cent centile of normal in 93 per cent of cases, compared with 57 per cent of cases for free beta-hCG and 32 per cent of cases for AFP. Combining free beta-hCG and PAPP-A or all three markers with maternal age would have the ability to detect 74 per cent of cases at a 0.5 per cent false positive rate (or 64 per cent at a 0.1 per cent false positive rate). Unlike in cases of trisomy 21, the low PAPP-A values observed in the first trimester are continued into the second trimester. Whether the good discriminatory power of PAPP-A can be realized in second trimester screening programmes will depend on developing two stage screening algorithms. This approach is unlikely to be better than the excellent detection rates achievable with free beta-hCG, PAPP-A and nuchal translucency in the first trimester.

Second trimester prenatal screening for Down's syndrome using alpha-fetoprotein and free beta hCG: a seven year review

OBJECTIVE

To determine the value and impact over a seven year period of a second trimester screening programme for trisomy 21 and trisomy 18, using the two maternal serum markers alpha-fetoprotein and free beta human chorionic gonadotrophin.

DESIGN

Retrospective review.

SETTING

A biochemical screening laboratory serving three health districts with three antenatal clinics in both teaching and nonteaching hospitals.

POPULATION

67,904 pregnancies in women of all ages screened between 14 and 22 weeks of gestation between 1 April 1991 and 31 March 1998.

METHODS

All women booked into three major antenatal clinics were offered biochemical screening. Women at increased risk of trisomy 21 or trisomy 18 (> or =1 in 250 at term) were offered an invasive diagnostic procedure. Follow up of the outcome of all pregnancies was performed.

MAIN OUTCOME MEASURES

Detection rate for trisomy 21 and trisomy 18, false positive rates, uptake of screening, uptake of amniocentesis in women identified at increased risk, prevalence of trisomy 21 at birth, detection and false positive rates by maternal age, fetal loss rate after amniocentesis, report turn around time, and identification of other anomalies.

RESULTS

Overall, 87% (67,904/78,501) of women underwent screening. The rate of detection of trisomy 21 was 75% (80/107; 95% CI 66 to 83) with a 5.1% false positive rate (3466/67,904; CI 4.9 to 5.3%). In women under 30 years of age the detection rate was 60% (18/30; CI 41 to 77) with a 2.6% false positive rate (956/36,371; CI 2.5 to 2.8). The rate of detection of trisomy 18 was 57% (8/14; CI 29 to 82) with a 0.7% false positive rate (475/67,904; CI 0.64 to 0.76). Uptake of amniocentesis was 83% (2912/3508). Women were 3.3 times more likely to refuse amniocentesis if the risk was close to the cutoff (1 in 250) than if the risk was > or =1 in 50. Fetal loss within 28 days of amniocentesis was 0.9% (25/2912). Prenatal screening identified 84 other anomalies in addition to 41 cases of impending fetal death.

CONCLUSION

Second trimester prenatal screening for trisomy 21 and trisomy 18 using a simple two marker approach incorporating free beta hCG can achieve high detection rates over a long period of time. Health authorities who still have not introduced trisomy 21 screening should be encouraged by what can be achieved and should consider making such screening available to all women. Established second trimester detection rates of 75% for a 5% false positive rate will be the benchmark by which first trimester screening using nuchal translucency, PAPP-A and free beta hCG will be judged.

Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In a study of 50 cases of trisomy 18 compared with 947 controls we have found the median multiple of the median (MoM) of maternal serum free beta human chorionic gonadotrophin to be significantly decreased (0.281 MoM) in samples collected between the 10th and 14th week of gestation. Similarly, maternal serum pregnancy associated plasma protein A (PAPP-A) levels are also decreased (0.177 MoM), whilst the median nuchal translucency is significantly higher (3.272 MoM). Free beta-hCG MoM was less than the 5th centile of normal in 64 per cent of cases of trisomy 18 and for PAPP-A was less than the 5th centile in 78 per cent of cases. Also, in 78 per cent of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, we predict that 89 per cent of cases of trisomy 18 could be detected at a 1 per cent false-positive rate. We conclude that specific trisomy 18 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21.

The influence of smoking on maternal serum PAPP-A and free beta hCG levels in the first trimester of pregnancy

In an analysis of 3111 singleton pregnancies routinely screened in the first trimester with nuchal translucency, free beta hCG and pregnancy associated plasma protein A (PAPP-A) smoking has been found to occur in 20.8 per cent of pregnant women. When the individual marker levels were assessed in smokers and non-smokers, levels of PAPP-A were reduced in smokers by some 15 per cent. Despite free beta hCG levels being reduced by 10-14 per cent in the second trimester of smoking women, in the first trimester period this is not evident. Simulation studies would suggest that in smokers the detection of trisomy 21 using free beta hCG, PAPP-A and maternal age will be reduced by some 5 to 6 per cent compared with that of the general population.

Second-trimester maternal urine human chorionic gonadotrophin beta-core fragment concentrations in Asian pregnancies with fetal chromosomal abnormalities

The aim of this study was to investigate the second trimester concentrations of maternal urine human chorionic gonadotrophin beta-core fragment (HCGbetacf) in Asian pregnanci2es with fetal chromosomal abnormalities. HCGbetacf concentrations were analysed from 34 urine samples in chromosomally abnormal pregnancies, including 28 cases of Down's syndrome, one case of trisomy 18, and five cases of other chromosomal abnormalities (one mosaic deletion and four translocations), and in a cohort of 268 normal pregnancies receiving second trimester amniocentesis. Results were normalized to urine creatinine (Cr) concentration and converted to the multiple of the median (MOM) concentration for the appropriate gestation. The median HCGbetacf MOM concentrations of Down's syndrome pregnancies (12.89) was significantly higher than that of normal pregnancies (1. 06) (P < 0.00001). Wide variations of HCGbetacf concentrations were observed in other chromosomally abnormal pregnancies. There were 18 of 28 (64%) Down's syndrome cases but one of five (20%) other chromosomally abnormal cases with HCGbetacf concentrations above the 95th centile of the control values (8.22 MOM cut-off). These findings suggest that HCGbetacf could be a potential marker in urine screening for fetal Down's syndrome in Asians.

Activation of alcohol-related associative networks by recent alcohol consumption and alcohol-related cues

AIMS

To investigate the influence of recent alcohol consumption and alcohol-related cues on performance in a sentence generation task.

DESIGN

Two experiments were carried out. In the first, the performances of light, moderate and heavy drinkers were compared. In the second, subjects were randomly assigned to one of three experimental treatments (alcohol-priming, non-alcohol priming, and control) and classified as light, moderate or heavy drinkers. The effect of experimental treatment, drinking status, gender and the interaction between these factors was studied.

SETTING

The experiments were carried out in quiet research rooms in psychology departments.

PARTICIPANTS

Volunteers recruited from university campuses.

MEASUREMENTS

Questionnaires were used to ascertain recent drinking histories. Subjects generated sentences incorporating ambiguous alcohol-related words which were provided by the experimenter. The sentences were then classified as alcohol-related or not, the dependent measure was the number of alcohol-related sentences produced.

FINDINGS

In both experiments heavier drinkers produced more alcohol-related sentences and males produced more alcohol-related sentences than females. In the second experiment more alcohol-related sentences were produced after subjects were exposed the alcohol priming condition.

CONCLUSIONS

The alcohol-related meaning of ambiguous words is more likely to be accessed by males and by heavier drinkers and after exposure to other alcohol cues.

Urine free beta-hCG and total estriol for Down syndrome screening during the second trimester in an Asian population

OBJECTIVE

To evaluate second-trimester free beta-hCG and total estriol (E3) in the maternal urine as markers for Down syndrome screening in an Asian population.

METHODS

Free beta-hCG and total E3 were measured in the urine samples of 28 Taiwanese Down syndrome pregnancies and 268 unaffected singleton pregnancies at 14-25 weeks. Results were normalized to urine creatinine concentrations and converted to multiples of the median (MoM) levels. Gestational ages were estimated by ultrasound measurements.

RESULTS

Median values of free beta-hCG, total E3, free beta-hCG to total E3 ratio, and the free beta-hCG to total E3 MoM ratio in Down syndrome pregnancies were 4.75 MoM, 0.66 MoM, 8.99 MoM, and 9.51, respectively. At a 5% false-positive rate, the observed detection rates were 36% (ten of 28) with total E3, 71% (20 of 28) with free beta-hCG, 68% (19 of 28) with free beta-hCG/total E3, and 71% (20 of 28) with free beta-hCG/total E3 MoM. When combined with maternal age, the expected detection rates were 65% with total E3, 71% with free beta-hCG, 76% with free beta-hCG/total E3, 80% with free beta-hCG/total E3 MoM, and 89% when combining free beta-hCG, total E3, and maternal age.

CONCLUSION

Urine free beta-hCG and total E3 are useful markers for Down syndrome screening during the second trimester in Taiwanese women.

A screening program for trisomy 21 at 10-14 weeks using fetal nuchal translucency, maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A

OBJECTIVE

To examine the potential impact of combining maternal age with fetal nuchal translucency thickness and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in screening for trisomy 21 at 10-14 weeks of gestation.

METHODS

Maternal serum free beta-hCG and PAPP-A were measured by Kryptor, a random access immunoassay analyzer using time-resolved amplified cryptate emission, in 210 singleton pregnancies with trisomy 21 and 946 chromosomally normal controls, matched for maternal age, gestation and sample storage time. In all cases the fetal crown-rump length and nuchal translucency thickness had been measured by ultrasonography at 10-14 weeks of gestation and maternal blood had been obtained at the time of the scan. The distributions (in multiples of the median; MoM) of free beta-hCG and PAPP-A (corrected for maternal weight) and fetal nuchal translucency (NT) were determined in the trisomy 21 group and the controls. Likelihood ratios for the various marker combinations were calculated and these were used together with the age-related risk for trisomy 21 in the first trimester to calculate the expected detection rate of affected pregnancies, at a fixed false-positive rate, in a population with the maternal age distribution of pregnancies in England and Wales.

RESULTS

In a population with the maternal age distribution of pregnancies in England and Wales, it was estimated that, using the combination of maternal age, fetal nuchal translucency thickness and maternal serum free beta-hCG and PAPP-A, the detection of trisomy 21 pregnancies would be 89% at a fixed false-positive rate of 5%. Alternatively, at a fixed detection rate of 70%, the false-positive rate would be 1%. The inclusion of biochemical parameters added an additional 16% to the detection rate obtained using NT and maternal age alone.

CONCLUSIONS

Rapid diagnostic technology like Kryptor, which can provide automated reproducible biochemical measurements within 30 min of obtaining a blood sample, will allow the development of interdisciplinary one-stop clinics for early fetal assessment. Such clinics will be able to deliver improved screening sensitivity, rapidly and more efficiently, leading to reduced patient anxiety and stress.

Calcified right atrial mass in a woman receiving long-term intravenous phosphate therapy

Right atrial masses are easily seen by 2-dimensional echocardiography and may represent primary tumors, secondary tumor invasion of the right atrium, tricuspid valve vegetations, or atrial thrombi. Calcification of right atrial masses is uncommon but easily identified by 2-dimensional echocardiography because of the high echogenicity of calcium deposits. We describe a patient with a heavily calcified right atrial thrombus caused by an indwelling central venous catheter and long-term intravenous phosphate infusion.

Urinary free beta hCG, beta core fragment and total oestriol as markers of Down syndrome in the second trimester of pregnancy

In a study of 69 random urine samples from cases of Down syndrome and 405 samples from unaffected pregnancies, we have assessed the value of various candidate markers that have been proposed as tools for screening for Down syndrome. We found that the marker urine free beta hCG in Down syndrome had a median MoM of 3.53 (95 per cent confidence interval 2.48-4.68) and at a 5 per cent cut-off would have identified 49 per cent (34/69) of cases. Urine beta core had a median MoM of 4.95 (3.87-8.62) and at a 5 per cent cut-off would have identified 39 per cent (27/69) of cases. Total oestriol had a median MoM of 0.65 (0.55-0.80) and at a 5 per cent cut-off would have identified 35 per cent (24/69) of cases. In conjunction with maternal age, the modelled detection rate increased to 55.8 per cent for free beta hCG, 49.8 per cent for beta core and 48.8 per cent for total oestriol. In combination free beta hCG, total oestriol and maternal age would have detected 68 per cent of cases for a 5 per cent false-positive rate. Using analyte ratios to obviate the need to correct for urine dilution in our study (rather than correcting to a fixed creatinine concentration) was not shown to be as effective as correcting using urine creatinine. Urine markers on the whole are unlikely to be of practical screening value considering the 85 per cent to 90 per cent detection rates achievable in the first trimester using a combination of ultrasound and maternal serum biochemistry.

Accuracy of Down's syndrome risks produced in a prenatal screening program

Down's syndrome screening in the second trimester using a variety of combinations of maternal serum markers has become an established part of antenatal care over the past decade. The methodology of calculating Down's syndrome risk using statistical models based on the Gaussian distribution functions of the various markers used is often considered daunting, and many screening centres rely on specific screening computer software to undertake the relevant calculations. Such software is often a closed system which does not allow the user to check or change any of the parameters within the model. It is clear from a recent UK NEQAS survey of Down's syndrome screening laboratories (Spencer, Ellis, Seth, 1997, unpublished data) that many centres are unsure what method of calculating risk and what population parameters are used in their software, and how appropriate these are for the population being screened. This confusion has led to uncertainty over the reliability of the risk estimates produced in Down's syndrome screening programs.

Evolution of an inhibin A ELISA method: implications for Down's syndrome screening

The development of a sensitive and specific enzyme-linked immunoassay (ELISA) for inhibin A stimulated the observation that inhibin A was a useful prenatal marker of Down's syndrome. Modifications of that ELISA, in terms of preassay sample treatment, detection methods and standard preparation, were subsequently introduced to improve assay performance and reduce costs. These modified formats have been validated and reported. We describe the modifications in detail, explaining the rationale for each, and report the results of a study directly comparing the various ELISA formats in terms of assay performance when applied to clinical samples and ability to differentiate between normal and Down's syndrome pregnancies. A format involving sample pretreatment with sodium dodecylsulphate at 100 degrees C was found to give better assay performance and a modest improvement in discrimination between Down's syndrome samples and controls, and we recommend this format for use by other investigators.

The influence of smoking on maternal serum AFP and free beta hCG levels and the impact on screening for Down syndrome

I have studied the impact of maternal smoking on the levels of maternal serum alpha-fetoprotein (AFP) and free beta human chorionic gonadotrophin (hCG) during the second trimester in a large series (30,727) of self-reported smokers and non-smokers whose pregnancy resulted in the birth of a normal fetus. I have confirmed in a smaller subset of this population that self-reporting is an accurate method of assessing smoking status as confirmed by biochemical (serum cotinine) assessment. In addition, I have investigated marker levels among 195 pregnancies affected by Down syndrome with smoking status confirmed by measurement of serum cotinine. In both unaffected and Down syndrome groups, the incidence of smoking was 19 per cent but a considerable variation was observed with maternal age when the incidence in younger women (under 25) was 32 per cent. AFP median levels in unaffected smokers were 3 per cent higher, whilst in the Down syndrome group smoker medians were increased by 10 per cent compared with the non-smoker group. Free beta hCG levels in unaffected smokers were reduced by 14 per cent, whilst in the Down syndrome group smoker median levels were decreased by 16 per cent. In the smoker group, the Down syndrome detection rate was 10 per cent lower than in the non-smoker group, whilst the false-positive rate was also 2 per cent lower. Correcting for smoking status would redress this inequality and produce an overall 2 per cent increase in the detection rate for a 0.4 per cent increase in the false-positive rate. This increase in screening performance may be worth building into screening programmes, particularly in populations with a high smoking incidence.

Precise gaussian distribution functions of maternal serum alpha-fetoprotein and free beta-subunit of human chorionic gonadotropin for trisomy 21 screening: improved accuracy for patient counseling

OBJECTIVE

Gaussian equation curves are used to generate baseline curves against which a priori maternal age Down syndrome risks are adjusted to develop likelihood ratios for individual patients. We sought to evaluate the accuracy of these calculations, minimize the affects of outliers, and to make improvements.

STUDY DESIGN

Gaussian distribution functions were used to investigate the best model for alpha-fetoprotein and free beta-human chorionic gonadotropin multiples of the median with use of nonlinear regressions. Parameters from distribution functions can be used to compute a more precise likelihood ratio for the decision logic for trisomy 21. A total of 58,297 normal cases and 348 cases of trisomy 21 were computed.

RESULTS

Log normal distribution functions generated by nonlinear regression produced excellent but exaggerated goodness of fit R2 to the frequency distributions of the data. For normal cases values were as follows (in mean, SD, and R2, respectively): log alpha-fetoprotein -0.07199, 0.15681, and 0.9970; log beta-human chorionic gonadotropin -0.15203, 0.24284, and 0.9987. For trisomy 21 cases the values were (in mean, SD, and R2, respectively) for log alpha-fetoprotein -0.19303, 0.15802, and 0.9828 and for log beta-human chorionic gonadotropin 0.19996, 0.29760, and 0.9669. Distributions reconstructed with use of statistical means and SDs generated goodness of fit R2 from 0.585 to 0.914. Use of means and SDs derived from distribution functions increased the R2 to 0.855 and 0.999. The change in the model produces, at a 5% false-positive rate, a sensitivity of 57.18% (199/348). A 1 in 113 cutoff point risk is obtained and is tighter than the 1 in 251 without the distribution functions, as versus 1 in 270 by age calculations alone.

CONCLUSIONS

Our data suggest that (1) normality of log transforms of alpha-fetoprotein and normality of log transforms of beta-human chorionic gonadotropin are reasonable models, (2) distribution functions can minimize the effect of outliers, which produces more realistic risk estimates, and (3) the effect of distribution functions versus standard mean and SDs cannot automatically be extrapolated to other parameters, which must be tested individually.