Ultrasound findings after screening for Down syndrome using the integrated test

OBJECTIVE: To evaluate the incidence and significance of fetal anomalies and "soft markers" after screening for Down syndrome using the integrated test. METHODS: This study is a retrospective study of 2,332 women at University College London Hospitals, United Kingdom. All women were screened for Down syndrome by the integrated test. Subsequently, a detailed anomaly scan was performed. All scan reports and screening results were analyzed statistically using SPSS 11.0 software. RESULTS: Sixty-eight (2.9%) patients were categorized as high risk. There were 12 cases affected by Down syndrome, 10 (10 of 68) in the high-risk group and two (two of 2,264) in the low-risk group. Soft markers or structural anomalies were found in 13.0% of the low-risk group, in 29.4% of the high-risk group, and in 50% of the fetuses affected by Down syndrome. Multiplying the likelihood ratio of each marker with the risk of Down syndrome from the integrated test reduced the false-positive rate of the integrated test from 2.5% to 1.8%, but was accompanied by a reduction in the detection rate from 83% to 75%. CONCLUSION: Absence of structural anomalies or markers should not prevent offering karyotyping to women in the high-risk group, because this would result in a significant reduction in the detection rate of Down syndrome. Women screened as low risk by the integrated test who have isolated soft markers should not be offered an amniocentesis.     

The introduction of the absolute risk for the detection of fetal aneuploidies in the first-trimester screening

Purpose: Maternal age is a crucial factor in fetal aneuploidy screening, resulting in an increased rate of false-positive cases in older women and false-negative cases in younger women. The absolute risk (AR) is the simplest way to eliminate the background maternal age risk, as it represents the amount of improvement of the combined risk from the maternal background risk. The aim of this work is to assess the performance of the AR in the combined first-trimester screening for aneuploidies.

Materials and methods: A retrospective validation of the AR in the combined first-trimester screening for fetal aneuploidies, in an unselected population at Altamedica Fetal-Maternal Medical Center in Rome, between March 2007 and December 2008.

Results: Of 3845 women included in the study, we had a complete follow-up on 2984. We evaluated that an AR Conclusions: In our study, the AR ameliorates the detection rate for aneuploidy. Further research and a prospective study on a larger population would help us to improve the AR in detecting most cases of aneuploidy.     

The evaporation test for detecting rupture of the fetal membranes

A method for detecting rupture of the fetal membranes, first described by Iannetta in 1984, has been tested. It is based on the heating of endocervical material on a glass slide to evaporate water, thus leaving a white residue if amniotic fluid is present and a brown residue if it is not. The method is simple, quick and inexpensive. The study showed the method to be reliable if the result is positive, but also to produce some false-negative results. Interpretation may in some cases be open to observer bias unless clearly positive. Positive results were seen as early as in week 26. This method may prove to be a valuable addition to other tests for detecting rupture of the fetal membranes.     

The significance of screening tests for aneuploidies in populations at low and high maternal-age-related risk

AIM: The aim of this study was to evaluate the validity of the triple test and the screen test in maternal populations at low and high maternal-age-related risk for fetal aneuploidy. METHODS: As a whole, 9,680 pregnant women at low risk and 627 at high risk underwent the triple test; 2,780 pregnant women at low risk and 408 at high risk underwent the screen or combined test; sensitivity, specificity, false positives and detection rate were compared between populations using Student's t-test. RESULTS: The triple test showed a detection rate of 75% in the low and 83.3% in the high risk population with a difference (P<0.003) for detection of trisomies 21 and 18 between the 2 populations; the screen test had a detection rates of 100% and 90% in the 2 populations, respectively, with a difference (P<0.005) between the 2 tests. CONCLUSIONS: Both tests are reliable for screening aneuploidies in the low risk population, the screen test having better performance; in the high risk population, the number of invasive procedures can be reduced by 78% with the triple test and by 84% with the screen test.     

Advanced first trimester screening (AFS): an improved test strategy for the individual risk assessment of fetal aneuploidies and malformations

Objective

First trimester risk assessment for fetal aneuploidies is computed on the base of a general background risk, which is depending on the maternal age. Thereby, the adjusted risk tends to rise with increasing age. Obversely, more unsuspicious fetal parameters [measurement of the nuchal translucency (NT) and biochemical parameters, free beta human chorionic gonadotropine (fß-Hcg) and pregnancy associated plasma protein A (Papp-A)] have to be observed to result in an unsuspicious test at higher age. It was the aim of this study to investigate the potential value of a novel risk assessment algorithm explicitly disregarding the maternal age.

Methods

This was an ultrasound cohort study of 1,463 singleton pregnancies at 11–14 weeks of gestation undergoing a first trimester screening for fetal aneuploidies by measuring the (NT), Papp-A and fß-hCG. In each case, the pregnancy outcome was obtained. Regarding either the detection of genetic affections or the combined detection of genetic or somatic anomalies, the test performance parameters (sensitivity, specificity, positive and negative predictive values) were calculated and compared with each other. For risk calculation the standard Fetal Medicine Foundation (FMF)-Software and an alternative software with a similar algorithm (JOY-Software) were utilized. Compared to this, the risk assessment had been modified by implementing a novel calculation algorithm (advanced first trimester screening algorithm, AFS) purposely disregarding the maternal age and again, the test performance parameters had been computed and were compared with the first ones.

Results

At the mere genetic analysis, all four test-strategies revealed to have identical sensitivity and negative predictive values. Compared to the standard FMF-Software, the JOY-Software showed a reduced false positive rate. In addition, in both softwares, the false positive rate is highly significant-reduced by implementing the AFS-algorithm. At combined genetic and somatic analysis, analogous results on different counts could be found.

Conclusion

In the effort to create an algorithm characterising somatic and fetal conditions of the fetus most properly, the inclusion of maternal age is not a helpful value and excluding the age from risk calculation leads to a high significant reduction of the false positive rate. Further, a comparable marked increase of both, specificity and positive predictive values, can be achieved for the FMF- and JOY-Software on the background of the generally more favourable JOY test performance.

     

Predictive value of increased nuchal translucency as a screening test for the detection of fetal chromosomal abnormalities

Objective.?The study aimed to estimate the incidence of increased nuchal translucency in the first trimester ultrasound scan results (cut-off limit 2.5 mm) and to evaluate the predictive value of increased nuchal translucency as a screening test for the detection of fetal chromosomal abnormalities.

Methods.?We used the ultrasound scan results of nuchal translucency evaluation and the results of chromosomal analysis of the invasive prenatal control performed as a result of increased nuchal translucency.

Results.?We collected 2183 nuchal translucency ultrasound scans in which we detected 21 embryos with a pathologic value (0.96%). We collected the data of 168 cases of invasive prenatal control due to increased nuchal translucency from which 122 cases were found. A total of 122 cases of pregnant women undergone an invasive prenatal diagnostic method due to increased nuchal translucency, of which 11 fetuses were found with trisomy 21 (Down syndrome) (9%), 3 fetuses with trisomy 13 (Patau syndrome) (2.45%), 3 fetuses with monosomy 45XO (Turner syndrome) (2.45%) and 1 fetus with translocation (0.8%).

Conclusions.?The positive predictive value of the increased fetal nuchal translucency as a screening test for the detection of fetal chromosomal abnormalities based on the results of the chromosomal-genetic analysis of the invasive prenatal diagnostic procedures is 14.8%.     

Uptake of prenatal screening for chromosomal anomalies: impact of test results in a previous pregnancy

AIM: To assess whether the uptake of prenatal screening for trisomy 21 in a subsequent pregnancy is influenced by being classified in the 'increased risk' or 'not at increased risk' group in the first pregnancy. SETTING: District General Hospital Maternity Unit. METHODS: Amongst a group of women attending for maternity care at this hospital, the maternity records were examined to find women having at least two pregnancies. Any prenatal screening record for each pregnancy was retrieved from the prenatal screening database. Prenatal screening for trisomy 21 was by a combination of maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG) in the second trimester and by maternal serum free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A) and fetal nuchal translucency (NT) thickness in the first trimester. Women were stratified according to their trisomy 21 risk into an 'increased risk' group (1: <250 in the second trimester and 1: <300 in the first trimester) or 'not at increased risk' group based on their first pregnancy. In a second pregnancy, the records were examined to see if the mother accepted prenatal screening in the second pregnancy. The rate of acceptance of screening in a subsequent pregnancy, depending on whether 'at increased risk' or 'not at increased risk' in the first pregnancy, was examined using chi square tests. RESULTS: In the second trimester study, 4601 women were identified with two pregnancies during the study period. Of these, 4559 women had prenatal screening in a subsequent pregnancy. Initially, 273 women were identified in the high-risk group, and of these 252 (92.3%) elected to have prenatal screening in a subsequent pregnancy. This compared with 4307 of 4328 (99.5%) women in the low-risk group. In the first trimester study, 1077 women were identified with two pregnancies during the study period. Of these, 1072 had prenatal screening in a subsequent pregnancy. Initially, 60 women were identified in the high-risk group, and of these 56 (93.3%) elected to have prenatal screening in a subsequent pregnancy. This compared with 1016 of 1017 (99.9%) in the low-risk group. Statistically, there was no difference between the rate of declining prenatal screening in a second pregnancy amongst those in the high-risk group in a first pregnancy or those in the low-risk group (p = 0.429 for second trimester screening and p = 0.794 for first trimester screening). Similarly, no difference could be demonstrated between rates when screening in the first or second trimester (p = 0.961) for those in the high-risk group. CONCLUSION: Despite the understandable anxiety associated with being identified in the high-risk group (as a false positive finding) in a previous pregnancy, this did not seem to deter women from accepting prenatal screening in a subsequent pregnancy.     

The best approach for early prediction of fetal gender by using free fetal DNA from maternal plasma

OBJECTIVES: Detection of free fetal DNA (ffDNA) in maternal blood during pregnancy has given rise to the possibility of developing new noninvasive approaches for early prenatal diagnosis.On a large-scale study, two protocols of real-time polymerase chain reaction (PCR) were compared in order to establish which Y-specific locus, either multicopy DYS14 or single copy SRY sequence, was the most suitable for developing a test with high diagnostic efficiency for early fetal gender assessment. The second aim was to assess whether the combination of the two detection systems could increase the performance of the prenatal test. METHODS: We analyzed 145 plasma samples from healthy pregnant women between 11 and 12 weeks of singleton gestation. For each sample, fetal gender was determined by using both protocols (DYS14 and SRY) during the same real-time PCR run. RESULTS: The data obtained by the DYS14 and SRY assays showed an efficiency in fetal gender prediction of 97.9 and 80%, respectively. It is not advisable to combine the two protocols because this association does not help in further improvements in fetal gender prediction. CONCLUSIONS: DYS14 assay is the best approach for early fetal gender assessment because it is more sensitive, accurate, and efficient than the SRY assay.     

Practical issues drawn from the implementation of the integrated test for Down syndrome screening into routine clinical practice

We have evaluated a cohort of women booked for antenatal care at University College London Hospitals. The uptake of screening was 64.4% and was significantly higher (73 versus 46%) in women who booked before 14 weeks. Of the women who booked before 14 weeks, 96.8% opted for the integrated test (IT). Overall, 5.3% failed to attend for the second blood test. The false-positive rate in the women who had the IT was 2.9%. All 11 cases of Down syndrome were detected prenatally. Our study is the first to evaluate implementation of the IT into routine clinical practice.     

Two years' prospective experience using fluorescence in situ hybridization on uncultured amniotic fluid cells for rapid prenatal diagnosis of common chromosomal aneuploidies.

A probe was generated from the YAC clone 831B9 that was suitable for the prenatal detection of trisomy 21 using fluorescence in situ hybridization (FISH). This probe was initially tested on a series of 650 unselected amniotic fluid samples prior to the karyotype being available. 630 were correctly identified as having two copies and 13 samples were correctly scored as having three copies of chromosome 21. Seven samples failed to produce a result. A trial was then initiated, reporting to clinicians the interphase FISH results before cytogenetic analysis had been performed. During the first 18 months of this trial 1504 samples were tested: 1467 were correctly identified as disomic and 35 samples were correctly scored as trisomic for chromosome 21. Two samples failed to produce a result. A chromosome 18 specific probe (LI.84) was employed where there was a relevant clinical indication (181 samples) and 10 samples were correctly scored as having three copies of chromosome 18. Thus, this approach appears to be reliable and is popular with both clinicians and patients due to the speed of the result. However, it does not replace chromosomal analysis on cultured cells, which detected a range of abnormalities besides the trisomies and triploidies detected by FISH.     

Accuracy of trisomy 18 screening using the second-trimester triple test

OBJECTIVE: To assess the accuracy of the calculated risk for trisomy 18 assigned to individual women screened with the second-trimester triple test. METHODS: The study was based on 382598 women screened in the Ontario Maternal Serum Screening Programme between October 1993 and September 2000. Of the women screened, 111 cases of trisomy 18 were identified. Originally, 92874 women were screened using a risk cut-off level method. Estimated risks of trisomy 18 were calculated by applying published population parameters for the remaining women screened using a fixed analyte cut-off method.Women were ranked according to their individual risk for trisomy 18 syndrome in decreasing order and divided into 12 groups. The mean calculated risks of having an affected pregnancy at term for each group were compared with the birth prevalence of the corresponding group after allowing for spontaneous fetal losses. RESULTS: Agreement between the mean calculated risks and the observed prevalence was seen across the entire risk range, although women identified as having high-risk pregnancies had an actual prevalence that was somewhat lower than that estimated by the screen. CONCLUSION: The calculated risk for trisomy 18 syndrome assigned to the individual woman on the basis of the risk cut-off method accurately reflects their risk of having a term trisomy 18 syndrome pregnancy.     

不同产前筛查方案对胎儿染色体异常检出效率的比较

目的 探讨不同产前筛查方案对胎儿染色体异常的检出效率.方法 应用时间分辨免疫荧光法对24986例孕妇进行母体血清学二联筛查,根据风险值及后续的检查方案不同将人群分为高风险直接进行羊水穿刺组(A1组)、高风险行无创产前检测(non-invasive prenatal testing,NIPT)组(A2组)、临界风险进行超...