[Clinical study of assessment of trisomy 21--precise risk evaluation in the first trimester of pregnancy]. / Eine klinische Studie zur Wertigkeit der Trisomie 21--Risikopräzisierung im ersten Trimester der Schwangerschaft.

BACKGROUND: In the past a non invasive risk analysis for detecting specific chromosomal aberrations was only possible from week 15 of pregnancy. In this paper the practicability of first trimester screening is analysed. MATERIAL AND METHODS: Blood samples were taken from 1000 pregnant women before a invasive prenatal diagnosis was performed. Total hCG, free beta-hCG and PAPP-A (pregnancy associated plasma protein A) was analysed. These data were combined with complete cytogenetic and ultrasonographic (CRL and nuchal translucency--NT) data. RESULTS: In more than 90% of cases the NT was below 3 mm. Here the rate of normal karyotypes was 97.8%. In 61 cases a abnormal karyotype was found. Here in the most cases we found an elevated NT. Also in the most cases of trisomy 21 and 18 and in triploidies a characteristic ratio of hCG/free beta-hCG and PAPP-A was discovered. Combining NT and biochemical analysis, 85% of trisomies 21 could be discovered as a risk group. CONCLUSIONS: This study demonstrates the possibilities of first trimester screening with a high detection rate for specific chromosomal aberrations. DISCUSSION: First trimester screening should only be performed in specialised centers because determination of NT and risk analysis needs extensive experience.

Assessment of fetal status in multiple gestation pregnancies using interphase FISH.

The use of fluorescence in situ hybridization (FISH) for women with multiple gestation pregnancies has been evaluated. Women were referred for chromosome analysis because of advanced maternal age, abnormal ultrasound findings or a positive family history and/or prior to fetal reduction. FISH was successfully applied to all specimens obtained by amniocentesis or chorionic villus sampling (CVS). Based on FISH results, fetal-fetal contamination of specimens following CVS was 11.5% in twin pregnancies and 16% in triplet or higher multiples. FISH detected trisomy 21 in three cases with no false negatives or positives. Whereas FISH may provide rapid and useful assessment of fetal status in decision-making regarding fetal reduction, the present study also highlighted the obstetrical difficulty of ensuring a sample representative of each fetus following CVS in addition to the possibility of not identifying clinically significant chromosome aberrations using currently available FISH probes.

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.

Individuals with abnormal phenotype and normal G-banding karyotype: improvement and limitations in the diagnosis by the use of 24-colour FISH.

The simultaneous identification, by fluorescence in situ hybridisation (FISH), of each chromosome in a distinct colour became feasible a few years ago. The key question in the application of this and many other developments in molecular cytogenetics to clinical situations is whether the results add significant further information that is relevant to the diagnosis. So far, limited data exist regarding how much improvement the technique brings to the diagnosis of phenotypically abnormal individuals in whom no abnormalities have been detected by conventional G-banding analysis. Because of the lack of a conclusive diagnosis, genetic counselling, estimation of recurrence risk and prenatal diagnosis of these individuals and their relatives is problematic. We report a study with 24-colour whole-chromosome painting of 10 familial and 11 isolated cases with abnormal phenotypes and normal G-banding karyotypes. Previously undetected unbalanced translocations were revealed in two cases. The value and current cost-effectiveness of multicolour FISH for cytogenetic diagnosis is discussed.

The long-term effect of external quality assessment on performance in service cytogenetics.

In 1993 a nationwide cytogenetic external quality assessment program (EQA) was initiated in the Federal Republic of Germany. Presently, some 70 laboratories, representing approximately 90% of all cytogenetic diagnostic tests, are participating in the study. Based on the quality assessment scheme of the Association of Clinical Cytogeneticists (1988) in the United Kingdom, quality of chromosome preparation and speed of routine diagnostic services are being evaluated. As a result of continuous external quality assessment, the mean banding level of participating laboratories rose from below 400 bands per haploid set (bphs) in 1994 to approximately 450 bphs in 1999 in prenatal tests and from about 400 to approximately 500 bphs in postnatal tests over the same 5-yr period. The percentage of participants achieving a banding level of 400 bphs or higher rose from approximately 50% to 93% in prenatal tests and from 60% to 96% in postnatal tests. No significant differences were observed in banding scores achieved by private laboratories compared to university institutes. The impact of the assessment of interpretation, reporting, and documentation remains difficult to evaluate. Preliminary data point to a more stringent adherence to ISCN nomenclature in karyotype designation by participants.

Diagnostic yield of the comprehensive assessment of developmental delay/mental retardation in an institute of child neuropsychiatry.

The Consensus Conference of the American College of Medical Genetics has established guidelines regarding the evaluation of patients with mental retardation (MR) [Curry et al., Am. J. Med. Genet. 72:468-477, 1997]. They emphasized the high diagnostic utility of cytogenetic studies and of neuroimaging in certain clinical settings. However, data on the diagnostic yield of these studies in well-characterized populations of individuals with MR are scant. Majnemer and Shevell [J. Pediatr. 127:193-199, 1995] attained a diagnostic yield of 63%. However, this study included only 60 patients and the classification included pathogenetic and causal groups. The Stella Maris Institute has evaluated systematically patients with developmental delay (DD)/MR and performed various laboratory studies and neuroimaging in almost all patients. We report a retrospective analysis of the diagnostic yield of 120 consecutive patients observed at our Institute during the first 6 months of 1996. There were 77 males and 43 females; 47 were mildly delayed (IQ 70-50), 31 were moderately delayed (IQ 50-35), and 42 were severely delayed (IQ 35-20). Diagnostic studies (history, physical examination, standard cytogenetics, fragile X testing, molecular studies, electroencephalography, electromyography, nerve conduction studies, neuroimaging, and metabolic screening tests) yielded a causal diagnosis in 50 (41.6%) and a pathogenetic diagnosis in 47 (39.2%) of the 120 patients. Causal categories included chromosomal abnormalities (14), Fra(X) syndromes (4), known MCA/MR syndromes (19), fetal environmental syndromes (1), neurometabolic (3) disorders, neurocutaneous (3) disorders, hypoxic-ischemic encephalopathy (3), other encephalopathies (1), and congenital bilateral perisylvian syndrome (2). Pathogenetic categories included idiopathic MCA/MR syndromes (35), epileptic syndromes (10), and isolated lissencephaly sequence (2). Diagnostic yield did not differ across categories and degree of DD. Our results, while confirming the diagnostic utility of cytogenetic/molecular genetic, and neuroimaging studies, suggest the usefulness of accurate electroencephalogram recordings, and stress the importance of a thorough physical examination. Referral to a university child neurology and psychiatry service, where a comprehensive assessment with a selected battery of investigations is possible, yields etiologic findings in a high percentage of DD/MR patients, with important implications for management, prognosis and recurrence risk estimate.

Aconselhamento genético para diagnóstico citogenetico em idade materna avançada: um estudo exploratório / Genetic counseling for invasive diagnostic procedures in advanced maternal age: an exploratory study

O acesso ao diagnóstico pré-natal profilatico de anomalias cromossômicas fetais a partir de procedimentos invasivos em pacientes de instituiçöes publicas brasileiras e fenômeno relativamente recente, e seu impacto ainda é desconhecido em nosso meio. O objetivo deste estudo foi verificar o grau de aceitaçäo do diagnóstico citogenético entre mulheres grávidas com idade superior a 35 anos, em hospital publico de uma universidade em Säo Paulo, e sua associaçäo com o nível sócio-econômico e cultural das pacientes. Método: Entrevistas semidirigidas foram realizadas com 80 pacientes antes e depois das consultas de aconselhamento genético, com o objetivo de avaliar o nível de conhecimento das pacientes e os motivos alegados para a decisäo de submeter-se ou näo ao procedimento invasivo; dados das consultas também foram analisados...

Prenatal diagnosis in Luxembourg.

Social and medical issues regarding prenatal diagnosis in Luxembourg are addressed. The organisation and the overall impact of amniocentesis on aneuploid births are described. Legal aspects are discussed as are future developments.

Prenatal diagnosis in Norway.

Prenatal diagnosis (PND) of genetic disorders is provided without costs to the woman or family, in Norway. However, the volume of examinations is significantly smaller than in most other Western European countries. Prenatal diagnosis because of relatively high maternal age is accepted only if the woman will be 38 years or older at the time of delivery. Adequate technologies and know-how are available. The limitations on the amount of work done in this field are a result of political decisions which may have been strongly influenced by fundamentalist groups. PND in Norway has reduced the number of infants born with anomalies of the autosomal chromosomes. The impact on births of infants with other disorders is very small.

Prenatal diagnosis in Portugal.

On practical terms we can say that prenatal diagnosis (PND) only started in Portugal in 1984 after the Abortion Act was approved by Parliament. Since then the demand for PND has been increasing, but we realise that the coverage of high-risk pregnancies as well as screening for fetal abnormalities in the general population are below the desirable levels. Among the factors that contribute to this we can mention the bad planning in some services, the low standard of ultrasound scans in the low-risk pregnancies, the small number of public cytogenetics laboratories performing fetal karyotyping, the scarcity of genetic counsellors and last but not least the inadequate limit of 16 weeks for termination of pregnancies in case of fetal malformation.

Prenatal diagnosis in Spain.

An overview of the national organisation of prenatal diagnosis (PND) in Spain is presented. Although PND is technically well developed and the number of prenatal services seems to be adequate, the uneven distribution between regions is reflected in a different prevalence reduction of chromosomal disorders and congenital malformations. Only about 41% or pregnant women use PND, with a wide range (14-64%) between regions. There is no national policy in PND or maternal serum screening for Down's syndrome, but local policies. As clinical genetics is not an officially recognised speciality, there is a shortage of clinical geneticists and it is difficult to organise PND activities and regulate them by law.

Prenatal diagnosis in Sweden: organisation and current issues.

Invasive prenatal diagnosis was introduced in Sweden in the early 1970s and is an integral part of the public health care system. Funding is provided by taxation; the patient only pays a consultation fee. Genetic analyses on a broad range of cytogenetic and molecular disorders are performed at the 6 university-affiliated hospitals and in 1 county hospital. About 6% of all newborns have been cytogenetically screened during pregnancy, and about 90% of the analyses are performed after amniocentesis. The main indication is chromosome analysis because of advanced maternal age.

Doppler assessment of umbilical flow after genetic amniocentesis.

The aim of our study was to evaluate the immediate changes on the fetal heart rate (FHR) and the fetal umbilical artery pulsatility index (UPI) after performing genetic amniocentesis. This was a prospective study including 431 consecutive singleton pregnancies between 14 and 18 weeks undergoing genetic amniocentesis in our institution. Doppler measurements were obtained transabdominally before and immediately after the procedure. Structural malformations detected by ultrasound were excluded. Student's t-test was performed for comparisons among different groups and observed mean changes. The results showed a significant decrease in FHR post-amniocentesis (mean 1.5 beats, t = 3.47, P < 0.01) and a non-significant elevation in UPI (mean -0.01, t = -0.29, P = 0.77) after the procedure. Differences in FHR could be found when analyzed by each gestational week. These preliminary data suggest that although acute fetal hemodynamic changes are detected after genetic amniocentesis, such changes are unlikely to have clinical relevance. However, it is reasonable to propose the use of Doppler as a method of assessing hemodynamic effects caused by prenatal invasive procedures in order to provide more accurate in vivo research on this issue.

FISH and PRINS, a strategy for rapid chromosome screening: application to the assessment of aneuploidy in human sperm.

The co-utilization of FISH and PRINS techniques for in situ chromosome screening was tested on human sperm nuclei. We used a centromeric repeat probe specific for chromosome 4 for FISH. PRINS reactions were performed with alpha-satellite primers specific for either chromosomes 9 or chromosome 18. Double labeling was obtained and estimates of disomy rates were carried out for the three chromosomes.

Use of decision analysis to evaluate patients' choices of diagnostic prenatal test.

Women with a family history of a chromosomal or genetic abnormality must weigh several factors in choosing between amniocentesis and chorionic villus sampling. We compared the prenatal test choices of three such women with those of decision analytic models that incorporated their preferences. Patient preferences were assessed using visual linear rating scales. Threshold analysis was used to determine preference ranges, and stochastic sensitivity analysis to provide confidence levels, for each choice of test. The test choices of patients and decision analytic models agreed in one case, and disagreed in two cases. In one of the latter two cases, stochastic and threshold analyses showed the disagreement to be slight; for small shifts in preference differences for first- vs. second-trimester diagnosis, or first- vs. second-trimester therapeutic abortion, patient and decision model would have agreed. In the other, stochastic analysis showed their differences to be large; there were no thresholds for early diagnosis, or for early therapeutic abortion, that would have led to agreement between patient and model. In the two cases in which patient and decision model agreed or slightly disagreed, the patients had made their own choice of prenatal test. In the case in which patient and decision model strongly disagreed, the patient's physician had shared in the choice of test. Decision analysis can be useful in analyzing prenatal test choices based on individual preferences for pregnancy outcomes. When choices of patients and decision models do not agree, examination of the locus of decision making (patient vs. physician) may help resolve apparent differences.

[Comparative analysis of the costs of cytogenetic techniques and molecular biology techniques in the diagnosis of fragile X disease]. / Analyse comparée du coût des techniques cytogénétiques et de biologie moléculaire dans le diagnostic de la maladie de l'X fragile.

Mental retardation is sometimes due to chromosomal abnormalities. Most frequent illnesses are Down syndrome and Fragile X syndrome. Using a cost analysis, we try to see what diagnosis method is the most relevant to find chromosomic causes for mental retardation in an institutionalized male population. Two techniques are compared: cytogenetic technique and molecular biology technique. Four diagnostic strategies are identified. They all have the same effectiveness, but, costs vary. Results depend on prevalence rates in the epidemiologic literature on Fragile X syndrome and other chromosomic abnormalities. The least-cost diagnostic strategy is molecular biology then constitutional karyotype in case of a negative result. This strategy costs about 600 FF1991 less compared with Fragile X karyotype and about 120 FF1991 less than when molecular biology is done in second, for fixed prevalence rates (i.e. Fragile X prevalence rate between 4.5 and 10% and other abnormalities between 2.2 and 25%). Fragile X karyotype strategy has the highest cost whatever the prevalence rates. Those results are discussed when introducing female population and delay to test results for prenatal diagnosis.

Fluorescent in situ hybridization utilization for high-risk prenatal diagnosis: a trade-off among speed, expense, and inherent limitations of chromosome-specific probes.

OBJECTIVE: The development of fluorescent in situ hybridization chromosome-specific probes has allowed the use of new fetal tissue collection techniques, such as fetal cells in maternal blood and coelocentesis--both of which, with current techniques, cannot generate complete karyotypes. We evaluated chromosome-specific probes for additional potential limitations in the setting of a high-risk prenatal diagnosis center. STUDY DESIGN: The last 24 months of fetal karyotypes from our prenatal cytogenetics laboratory were analyzed for those abnormalities that should be detectable by chromosome-specific probes and those that would likely be missed. RESULTS: In 6006 karyotypes 207 (3.4%) abnormalities were found, of which 104 were common trisomies, 12 triploidies, and 19 monosomies that would have been detected with current probe combinations (13, 18, 21, X, and Y) (135/207, 65.2%). Seventy-two abnormalities (35%) represented other trisomies (16/207, 7.7% for 9, 12, 15, 16) and rearrangements (inversions, translocation markers were 56/207, 27.1%), which would have been missed. CONCLUSIONS: Use of current fluorescent in situ hybridization chromosome-specific probes protocols would have detected only 65% of chromosome abnormalities in our high-risk population. Incomplete ascertainment must be weighed against the cost and speed of fluorescent in situ hybridization chromosome-specific probes when comparing it with traditional karyotyping. Although this new technique may prove useful in low-risk screening programs (fetal cells in maternal blood), its current use in high-risk populations should be questioned until its sensitivity is expanded to identify more subtle and less common chromosomal abnormalities.