Assessment of the value of reporting partial screening results in prenatal screening for Down syndrome

Urinary Proteomics for Noninvasive Prenatal Screening of Trisomy 21: New Biomarker Candidates

Trisomy 21 is a common birth defect in humans. Screening for trisomy 21 is one of the most important tasks in routine prenatal care and robust noninvasive diagnostics are needed in clinical practice. Urinary proteomics offers a new research platform for diagnostics innovation in this context. We report here new biomarker candidates using urinary proteomics profiling. Specifically, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze the proteomes of urine samples from 19 pregnant women (aged 28-44 years) carrying fetuses with trisomy 21 and 22 healthy pregnant women (aged 27-42 years) carrying fetuses with normal karyotype. We identified more than 50 differentially expressed proteins between the trisomy 21 group and healthy group, and most of these proteins were associated with the embryonic development. Importantly, tissue inhibitor of metalloproteinases 2 (TIMP2) and lysosomal-associated membrane protein 2 (LAMP2) were further selected as potential urinary protein biomarkers. We found that the combination of TIMP2 and LAMP2 could differentiate fetuses with trisomy 21 from healthy controls with a sensitivity of 74%, a specificity of 82%, and an area under the receiver operating characteristic curves (AUC) value of 0.82 (95% confidence interval, 0.69-0.95). We conclude that TIMP2 and LAMP2 offer promise as biomarker candidates and warrant further clinical research in larger study samples. These findings further our understanding of the pathological processes involved in fetal trisomy 21 and are poised to accelerate the development of new noninvasive potential biomarkers for trisomy 21 prenatal screening.

Quantitative analysis of total β-subunit of human chorionic gonadotropin concentration in urine by immunomagnetic reduction to assist in the diagnosis of ectopic pregnancy

BACKGROUND

The initial diagnosis of ectopic pregnancy depends on physical examination, ultrasound, and serial measurements of total β-subunit of human chorionic gonadotropin (hCGβ) concentrations in serum. The aim of this study was to explore the possibility of using quantitative analysis of total hCGβ in urine rather than in serum by immunomagnetic reduction (IMR) assay as an alternative method to diagnose an ectopic pregnancy.

METHODS

We established a standard calibration curve of IMR intensity against total hCGβ concentration based on standard hCGβ samples, and used an IMR assay to detect total hCGβ concentrations in the urine of pregnant women with lower abdominal pain and/or vaginal bleeding. The final diagnosis of ectopic pregnancy was based on ultrasound scans, operative findings, and pathology reports. In this prospective study, ten clinical samples were used to analyze the relationship of total hCGβ IMR signals between urine and serum. Furthermore, 20 clinical samples were used to analyze the relationship between urine IMR signals and serum levels of total hCGβ.

RESULTS

The calibration curve extended from 0.01 ng/mL to 10,000 ng/mL with an excellent correlation (R(2)=0.999). In addition, an excellent correlation of total hCGβ IMR signals between urine and serum was noted (R(2)=0.994). Furthermore, a high correlation between urine IMR signals and serum levels of total hCGβ was noted (R(2)=0.862).

CONCLUSION

An IMR assay can quantitatively analyze total hCGβ concentrations in urine, and is a potential candidate for point-of-care testing to assist in the diagnosis of ectopic pregnancy.

Sonographic markers for early diagnosis of fetal malformations

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

Ethical considerations in first-trimester Down syndrome risk assessment

PURPOSE OF REVIEW

First-trimester risk assessment has now become sophisticated and of increasing relevance and applicability to decision-making by pregnant woman about invasive diagnosis. Ethics is an essential dimension of understanding this relevance and applicability. This paper addresses the ethical dimensions of first-trimester risk assessment for trisomy 21.

RECENT FINDINGS

It is now well established in the ethics and law of the informed consent process that physicians are obligated to offer to patients all medically reasonable alternatives for managing the patient's condition. This disclosure should be guided by the reasonable person standard: the physician should provide clinically important information about the patient's condition or diagnosis, the medically reasonable alternatives for managing it, and the clinical benefits and risks of each such alternative.

SUMMARY

On the basis of the ethics of informed consent, we argue that routinely offering first-trimester risk assessment in centers qualified to provide it is ethically obligatory. We describe how pregnant women can be expected to respond to this offer. We then argue that routinely withholding the results of first-trimester risk assessment is ethically unjustified. The ethics of informed consent is an essential dimension of first-trimester risk assessment for trisomy 21.

Ethics is an essential dimension of first-trimester risk assessment for trisomy 21

We identify the clinical implications of the ethics of informed consent for risk assessment for trisomy 21. Based on the ethics of informed consent, we argue that routinely offering first-trimester risk assessment in centers qualified to provide it is ethically obligatory. We describe how pregnant women can be expected to respond to this offer. We then argue that routinely withholding the results of first-trimester risk assessment is ethically unjustified. The ethics of informed consent is an essential dimension of first-trimester risk assessment for trisomy 21.

Patient preference regarding first-trimester aneuploidy risk assessment

OBJECTIVE

We assessed patient views regarding disclosure of first-trimester Down syndrome risk assessment results compared with withholding results until a single, more accurate second-trimester screening result is available.

STUDY DESIGN

A prospective, institutional review board-approved, voluntary, anonymous survey was presented to patients with singleton pregnancies who were undergoing first-trimester nuchal translucency and biochemical screening at our institution. Options included immediate (sequential testing) or later disclosure (integrated testing). Descriptions and a comparison of the options were included in the survey.

RESULTS

One hundred one women completed the questionnaires; 69.3% of the patients preferred sequential testing, compared with 30.7% of the patients who were either unsure or preferred integrated testing. Older patients and those patients with better background knowledge of screening tests preferred earlier disclosure of screening results (P = .035 and P = .026, respectively). Patients who preferred earlier disclosure also preferred termination of a Down syndrome pregnancy (P = .013).

CONCLUSION

Older patients and those patients with a better understanding of screening tests preferred immediate disclosure of first-trimester risk assessment results; these women were more likely to prefer to terminate an affected pregnancy.

[Role of "subtle" ultrasonographic signs during antenatal screening for trisomy 21 during the second trimester of pregnancy: meta-analysis and CPDPN protocol of the Grenoble University Hospital]

OBJECTIVE

A meta-analysis about subtle ultrasonographic signs in second trimester of pregnancy.

MATERIALS AND METHODS

196 articles dealing with the subject--from 1985 to July 2002--were studied. Data on the 11 reported signs were collected from 92 theoretically and/or statistically valid studies. Then, the studies were selected according to several criteria: isolated characteristic, defined thresholds, calculable sensitivity and specificity. After checking for homogeneity, a likelihood ratio was calculated for some of the signs.

RESULTS

This meta-analysis of the second trimester ultrasonographic signs of Down's syndrome enabled us to estimate the likelihood ratio (LHR) of six signs. At 22 weeks'gestation (WG) these signs are: pyelectasis equal to or greater than 5 mm; nuchal fold thickness equal to or greater than 6 mm; persistence of choroid plexus cysts; shortness of the femur and humerus below the tenth percentile; hyperechogenic bowe; and nasal bone length less than 2.5 mm.

CONCLUSION

These validated ultrasonographic signs are independent of nuchal translucency thickness at 12 WG and of maternal serum biochemistry. This allows to calculate a combinate risk for nuchal translucency, maternal serum biochemistry and second trimester ultrasonographic signs when they are validated.

Clinical implications of the ethics of informed consent for first-trimester risk assessment for trisomy 21

OBJECTIVE

We identify the clinical implications of the ethics of informed consent for risk assessment for trisomy 21.

FINDING

Based on the ethics of informed consent, we find that routinely offering first-trimester risk assessment in centers qualified to provide it is ethically obligatory, and routinely withholding the results of first-trimester risk assessment is ethically unjustified.

CONCLUSION

The ethics of informed consent is an essential dimension of first-trimester risk assessment for trisomy 21.

Practical strategies in contingent sequential screening for Down syndrome

OBJECTIVE

To design and assess the performance of protocols for contingent sequential Down syndrome screening that can be implemented in practice.

METHODS

Protocols were designed in which all women received first-trimester measurement of nuchal translucency (NT) together with maternal serum pregnancy-associated plasma protein-A (PAPP-A) and either free beta- or total human chorionic gonadotrophin (hCG). Those women with borderline Down syndrome risks received follow-up second-trimester maternal serum involving double, triple, or quadruple serum screening markers: alpha-fetoprotein, free beta-hCG or total hCG, unconjugated estriol and inhibin-A. Specific ranges of risks were used to define the borderline group. Separate protocols were developed for the United Kingdom and the United States to reflect differences in commonly used tests, cut-offs, and the gestational age at testing. Detection rates and false-positive rates were estimated by multivariate Gaussian modelling with Monte Carlo simulation.

RESULTS

Proposed protocols based on first-trimester NT, PAPP-A and free beta-hCG or total hCG, followed by selective use of second-trimester quadruple markers can result in a 91% detection rate and 2.1% false-positive rate for the United Kingdom and a detection rate of 89% and false-positive rate of 3.1% for the United States. For both countries, over 60% of affected pregnancies would be detected in the first trimester and less than 20% of women would require a second-trimester Down syndrome risk assessment. Use of alternative cut-offs to define those with borderline risks or different combinations of second-trimester markers also yielded high detection rates and low false-positive rates.

CONCLUSION

With appropriate patient counselling, it should be possible to provide highly effective Down syndrome screening using contingent sequential protocols.

First-trimester screening for aneuploidy

Prenatal screening for aneuploidy in the first trimester using novel ultrasound and maternal serum markers represents a promising improvement over the currently available second-trimester screening methods. This article reviews the current status of first-trimester screening for Down syndrome and other aneuploidies and explores the issues related to implementing first-trimester screening into mainstream prenatal care in the United States.

A model for disclosing the first trimester part of an integrated Down's syndrome screening test

This study was designed to evaluate a model for disclosing the first part of an integrated Down's syndrome (DS) test without affecting its low false-positive results. Parturient women underwent sequential DS-screening tests. They included nuchal translucency (NT) and biochemistry assessments in the first trimester and a mid-gestation triple test. Although screening tests results were given following each test, fetal karyotyping was performed by means of mid-gestation amniocentesis. The proposed approach for disclosure refers to either (a) cases picked by a statistical model (this is based on a logistic regression analysis and a receiver-operated curve that was set to a specificity of 100% of first-trimester markers pointing on at very high probability of aneuploidy) or (b) cases demonstrating a first trimester DS risk > or = 1 : 40 (a threshold level at which the integrated test results will always be screen positive). The results of the sequential screening and pregnancy outcome were available for 372 normal and 22 chromosomal affected singletons. NT and pregnancy-associated placental protein A emerged as the most sensitive marker combination. The statistical model picked up seven of 22 abnormal cases (32%), and a first-trimester DS risk > or = 1 : 40 was detected in 11 (50%) (there was an overlap of five cases). The combined strategy yields a 60% detection rate (13/22) of the affected pregnancies and without any increase in the false-positive results. This can be achieved immediately following the first part of the integrated DS test. This model obviates the ethical, clinical, and financial implications of further assessing about 60% of the affected pregnancies.

Screening for aneuploidy in twins and higher-order multiples: is first-trimester nuchal translucency the solution?

Screening for aneuploidy in twins and higher-order multiples present complex practical and ethical issues that limit its provision to women. We review the currently available screening options and compare the merits and disadvantages of each method. The available diagnostic tests and therapeutic interventions for screen positive cases are also reviewed.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to list the various screenings for Down syndrome during pregnancy, to outline the advantages and disadvantages of each screening method, and to summarize the challenges in screening for aneuploidy in twins.

Advances in prenatal screening for Down syndrome: II first trimester testing, integrated testing, and future directions

BACKGROUND

The acceptability of prenatal screening and diagnosis of Down syndrome is dependent, in part, on the gestational age at which the testing is offered. First trimester screening could be advantageous if it has sufficient efficacy and can be effectively delivered.

ISSUES

Two first trimester maternal serum screening markers, pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG), are useful for identifying women at increased risk for fetal Down syndrome. In addition, measurement of an enlarged thickness of the subcutaneous fluid-filled space at the back of the neck of the developing fetus (referred to as nuchal translucency or NT) has been demonstrated to be an indicator for these high-risk pregnancies. When these three parameters are combined, estimates for Down syndrome efficacy exceed those currently attainable in the second trimester. Women who are screen-positive in the first trimester can elect to receive cytogenetic testing of a chorionic villus biopsy. The first trimester tests could also, theoretically, be combined with the second trimester maternal serum screening tests (integrated screening) to obtain even higher levels of efficacy. There are, however, several practical limitations to first trimester and integrated screening. These include scheduling of testing within relatively narrow gestational age intervals, availability of appropriately trained ultrasonographers for NT measurement, risks associated with chorionic villus biopsy, and costs. There is also increasing evidence that an enlarged NT measurement is indicative of a high risk for spontaneous abortion and for fetal abnormalities that are not detectable by cytogenetic analysis. Women whose fetuses show enlarged NT, therefore, need first trimester counseling regarding their Down syndrome risks and the possibility of other adverse pregnancy outcomes. Follow-up ultrasound and fetal echocardiography in the second trimester are also indicated.

CONCLUSION

First trimester screening appears to be a highly effective method to screen for Down syndrome. Women with screen-positive results based on NT measurement appear to be at increased risk for diverse fetal abnormalities. The finding of a normal fetal karyotype may not, therefore, carry a high level of reassurance for a normal baby.