Rapid prenatal diagnosis of aneuploidies in uncultured amniocytes by fluorescence in situ hybridization. Evaluation of >3,000 cases.

OBJECTIVE: A new method in prenatal diagnostics allows to demonstrate certain numeric chromosomal aneuploidies in amniotic cells within 24 h in contrast to conventional methods which take 1-3 weeks. MATERIALS: The experience with this rapid fluorescence in situ hybridization (FISH) method is compared to standard karyotyping and its clinical relevance is described in a large clinical pilot study. FISH on uncultured amniocytes has been performed from 12 weeks of gestation to the third trimester using commercially available chromosome-specific DNA probes for chromosomes 13, 18, 21, X and Y. RESULTS: FISH was performed successfully in 3,150 prenatal cases. All trisomies 13, 18 and 21 and all cases with gonosomal aberrations were detected by FISH analysis. Neither false-positive nor false-negative results were obtained using FISH. For all analyzable disorders the FISH results were in complete agreement with standard cytogenetics. CONCLUSIONS: In our experience, FISH is a valuable and reliable method for rapid diagnosis of numeric chromosomal aneuploidies.     

Rapid prenatal diagnosis of trisomy 21 in 5049 consecutive uncultured amniotic fluid samples by fluorescence in situ hybridisation (FISH).

OBJECTIVES: This was a retrospective study on the results of interphase fluorescence in situ hybridization (FISH), performed routinely for chromosome 21 and on ultrasonographic indications for chromosomes 13, 18, X and Y in a series of 5049 amniotic fluid samples. METHODS: Interphase FISH for chromosome 21 was performed in 5049 consecutive amniotic fluid samples for the rapid prenatal diagnosis of Down syndrome. Aneuploidy for four other chromosomes (13, 18, X and Y) was tested following ultrasonographic indications. Karyotypes from standard cytogenetic analysis were compared to the FISH results. RESULTS: Using conventional cytogenetics 3.6% (183/5049) chromosomal anomalies were detected. After exclusion of familial chromosome rearrangements, i.e. balanced autosomal reciprocal or Robertsonian translocations (30/5049) and inversions (19/5049), 2.65% chromosomal anomalies (134/5049) were diagnosed. Of this group 0.18% (9/5049) were chromosomal rearrangements not detectable by FISH and 2.47% (125/5049) were numerical chromosomal anomalies detectable by interphase FISH for chromosomes 13, 18, 21, X and Y. With routine interphase FISH for chromosome 21 and FISH on echographic indication for the other four chromosomes we detected 107/125 of these numerical chromosomal anomalies, i.e. 85.6%. All 70 cases of trisomy 21 were detected by FISH and confirmed with conventional cytogenetics (sensitivity=100%) and there were no false-positive results (specificity=100%). Maternal cell contamination of amniotic fluid samples occurred in 1.27% (64/5049) of samples; 0.26% (13/5049) of these samples were uninformative by FISH due to maternal cell contamination (12/5049) or absence of nuclei in one sample (1/5049). CONCLUSION: In this group of 5049 samples we found that FISH is a reliable technique for the rapid prenatal diagnosis of trisomy 21. The number of uninformative cases due to maternal cell contamination was low. The strategy to perform FISH for chromosome 21 in all samples and only on ultrasonographic indication for the four other chromosomes (13, 18, X and Y) followed by standard cytogenetics is effective.     

FISH analysis of fetal nucleated red blood cells from CVS washings in cases of aneuploidy.

OBJECTIVE: In chorionic villus sampling (CVS) the chromosome analysis is inconclusive in 1-2% of the samples. In many cases follow-up amniocentesis is performed. Fetal nucleated red blood cells (FNRBCs) are present in washings of chorionic villus samples. We wanted to establish whether analysis of these true fetal cells, using fluorescence in situ hybridization (FISH), could support the CVS karyotype. METHODS: We analysed washings of first trimester chorionic villi from non-mosaic 45,X (n=6) and full trisomy 18 cases (n=7). FNRBCs were identified by immunostaining and FISH was performed with chromosome-specific probes for X, Y and 18. RESULTS: In all 13 samples FNRBCs were present (between 4 and 30 cells per sample). Five cases of monosomy X showed one X signal in 89-100% of the nuclei; in the other case 50% of the nuclei displayed one signal. In the trisomy 18 cases three spots were seen in 60-100% of the cells. CONCLUSION: The CVS aneuploidy was confirmed in FNRBCs in all samples, so FISH on FNRBCs can be used in cases of non-mosaic numerical chromosomal abnormalities. This test can confirm a CVS diagnosis of monosomy X or trisomy 18 and thus minimize the risk for false-positive diagnoses. An additional invasive test may be prevented.     

Rapid-FISH--fast and reliable method of detecting common numerical chromosomal aberrations in prenatal diagnosis

OBJECTIVE: In recent years, new possibilities of prenatal diagnosis have opened up, due to the development of techniques which guarantee shorter time of obtaining results. One of those methods, called Rapid-FISH (rapid fluorescence in situ hybridization), for detecting numerical aberrations of chromosomes 13, 18, 21, X and Y without culturing, enables to have the results in 2-5 days. The time necessary to obtain fetal karyotype result with the usage of the classical cytogenetic methods is about 2-3 weeks and depends mainly on the culture growth rate. DESIGN: The aim of the study was to evaluate the effectiveness of the Rapid-FISH technique in detecting numerical chromosome aberrations of 13, 21, 18, X and Y in amniocytes' nuclei from amniotic fluid. MATERIALS AND METHODS: Rapid-FISH and cytogenetic analysis has been performed for 161 pregnancies in the Department of Genetics at Wroclaw Medical University during years 2005 and 2006. The FISH was performed using AneuVysion kit (Vysis), according to a standard protocol. RESULTS: All normal and abnormal results were confirmed by classical cytogenetic method (GTG banding and karyotyping). Additional chromosomal aberrations, not possible to be detected in FISH, were observed in case of two patients with normal results from FISH analysis. CONCLUSIONS: Rapid-FISH is a reliable and fast method for detecting numerical chromosomal aberrations in prenatal diagnosis and should be implemented as a routine diagnostic procedure in pregnancies with high risk of fetal aneuploidy (of chromosomes 13, 18, 21, X i Y).     

Efficient combined FISH and PRINS technique for detection of DAZ microdeletion in human sperm

Intracytoplasmic sperm injection (ICSI) now offers an effective therapeutic option for men with male infertility and is believed to allow transmission of genetically determined infertility to the male offspring. Transmission of DAZ (Deleted in Azoospermia) microdeletion is one of the major concerns for oligo and severe oligozoospermia patients. Screening of the Y chromosome microdeletion in the diagnostic work-up of infertile men is mainly done using polymerase chain reaction (PCR) on blood leukocytes. However, there are evidences showing that presence of DAZ in somatic cells might not be indicative of its presence in germ cell lineage. In this report we are going to describe a combined Primed in situ labeling (PRINS) and fluorescence in situ hybridization (FISH) technique to show the localization of DAZ gene as well as Y chromosome centromere on sperm nuclei. PRINS is a combination of FISH and in situ polymerization provides another approach for in situ chromosomal detection. In the present study the PRINS primers specific for DAZ genes and traditional direct labeled centromere FISH probes for Y and X chromosomes were used in order to simultaneously detect DAZ genes and sex chromosome aneuploidy in sperm samples.     

The clinical application of interphase FISH in prenatal diagnosis

Fluorescence in situ hybridization (FISH) for five chromosomes (13, 18, 21, X and Y) detected 87 of 107 (81%) of the chromosome aberrations identified by conventional chromosome analysis applied to fetal interphase cells obtained by chorionic villus sampling or amniocentesis. The choice of FISH was solely determined by prospective parents after formal genetic counselling concerning the advantages and disadvantages of FISH analysis. Excluding known familial chromosome aberrations, if FISH analysis revealed normal signals, there was an overall residual risk of 1 in 149 for an undetectable chromosome aberration. This risk varied according to the indication for prenatal diagnosis: 1 in 177 for women of advanced maternal age; 1 in 60 for women at increased risk for Down syndrome based on maternal serum screening; and, 1 in 43 for women whose ultrasound examination revealed fetal anomalies. There were 20 cases of discordance between the FISH results and standard karyotype analysis: four were the outcome of a failure to apply the appropriate FISH probe; 16 were not detectable by the available FISH probes. Of these 16, nine were chromosome abnormalities with clinical significance and seven were familial. If FISH is to become a standard part of prenatal genetic diagnosis, genetic counselling that is sensitive to patient health needs must be based on accurate information about the biological and obstetrical implications of the results of FISH analysis.     

Familial X centromere variant resulting in false-positive prenatal diagnosis of monosomy X by interphase FISH.

Interphase fluorescent in situ hybridization (FISH) analysis performed on uncultured amniotic fluid cells from a female fetus revealed a single signal using an X chromosome alpha-satellite probe, and the absence of any signal using a Y chromosome alpha-satellite probe. This result was initially interpreted as monosomy for the X chromosome in the fetus. Subsequent chromosome analysis from the cultured amniotic fluid cells showed two apparently normal X chromosomes. FISH using the X alpha-satellite probe on metaphase spreads revealed hybridization to both X chromosomes, although one signal was markedly reduced compared to the other. The same hybridization pattern was observed in the mother of the fetus. This is the first report of a rare familial X centromere variant resulting in a false-positive diagnosis of monosomy X by interphase FISH analysis for prenatal diagnosis.     

Evaluation of sex chromosome aneuploidies in women with Turner's syndrome by G-banding and FISH. A serial case study

OBJECTIVE: To evaluate sex chromosome aneuploidies in patients with Turner's syndrome using two cytogenetic techniques. STUDY DESIGN: A sample of 35 women with a clinical suspicion of Turner syndrome was examined in the Hospital of Obstetrics and Gynecology, Instituto Mexicano del Seguro Social, Monterrey, Mexico. They were subjected to a conventional cytogenetic technique with G-banding and to fluorescence in situ hybridization (FISH) using a specific alpha satellite X chromosome (DXZ1) and specific alpha satellite Y chromosome (DYZ1). RESULTS: Using both techniques, 17 cases (48.57%) showed the same karyotype. Using FISH: (1) in 8 cases the presence of the Y chromosome was confirmed, (2) in 18 cases (51.43%) a new cell line was identified, (3) in 2 cases (5.71%) the derivative X was clarified, and (4) in 3 cases (8.57%) the origin of the chromosome markers (1 of X chromosome and 2 of Y chromosome) was delineated. FISH highlighted the differences between the initial diagnosis, based on G-banding, and the final diagnosis, determined by specific probes for the X and Y chromosomes. CONCLUSION: FISH is a useful tool in the detection of low-frequency cell lines and identification of the nature and origin of derivative chromosomes and unknown chromosome markers that have important implications for the treatment of patients with Turner's syndrome.     

Correlation of abnormal rapid FISH and chromosome results from amniocytes for prenatal diagnosis

Rapid fluorescence in situ hybridization (FISH) performed on 1,788 amniocenteses, using Aneuvision (Vysis) probes for chromosomes 13, 18, 21, X, and Y, over several years, yielded 115 cases with percentages of aneuploidy between 4 and 100%. All cases above 60% were confirmed to be positive by chromosome analysis. Fifteen of forty-one cases that would be considered inconclusive by generally accepted criteria (i.e. with less than 60% of cells with an abnormal signal pattern) revealed lower cutoffs to be positive when confirmed by chromosome analysis. For trisomy 21, 6 cases with percentages from 36 to 57% were positive; 4 of 7 cases with percentages from 22.5 to 33% were positive; 11 cases with percentages of 13% or less were negative. Similar trends were found for aneuploidies of 13, 18, X, and Y. However, the number of abnormal cases is still too small to determine definitive cutoffs in the <60% gray zone. An average of 57 metaphases was analyzed for cases with FISH percentages below 60%. Despite the wide range of abnormal FISH percentages for chromosomally positive cases, we found no examples of autosomal mosaicism in this series. Although sex chromosome mosaicism was cytogenetically evident in several cases, there was little direct correlation between cytogenetic and rapid FISH results. FISH results involving sex chromosomes were more frequently confounded by maternal cell contamination and other technical factors.     

应用荧光原位杂交技术诊断羊水细胞染色体异常

探讨荧光源位杂交技术于产前诊断羊水细胞染色体异常的实验方法的应用价值。方法对３４例孕１６－２３周有产前认旨征者经腹部抽取羊水,用Ｃｈａｎｇ培养液传代培养,常规制备羊水细胞分裂中期染色体,应用生物素及地高辛标记的人类全着线粒探针和Ｘ、Ｙ、１３、２１、１８号染色体     

Is cytogenetic diagnosis of 46,XX karyotype spontaneous abortion specimens erroneous? Fluorescence in situ hybridization as a confirmatory technique

AIM: Performing the standard cytogenetic technique on spontaneous abortion material is still a valuable tool, but finding a normal 46,XX karyotype can confuse investigators and lead to a problem in diagnosis. This is mainly because it is possible for the female or male conceptus to retain contaminating maternal cells. To address this possibility, we used fluorescence in situ hybridization technique (FISH). X (DXZ1: p11.1-q11.1 region) and Y (DYZ3: p11.1-q11.1 region) chromosome alpha-satellite probes were employed to confirm the karyotypes previously diagnosed as 46,XX by our cytogenetic laboratory, or to verify the occurrence of 'Y chromosome component'. METHODS: Besides conventional long-term tissue cultures and G-bands by trypsin using Giemsa (GTG) bandings, FISH analyses were also performed. RESULTS: A total of 134 spontaneous abortion specimens (singleton gestations) were referred for cytogenetic evaluation, of which 125 specimens were successfully karyotyped. Of these, 20.8% (26/125) had chromosome aberrations; 88.5% (23/26) of these aberrations were numerical and 11.5% (3/26) were structural. The most prevalent numerical anomalies were trisomies 15, 16 and 21, tetraploidies, triploidies and monosomy X. FISH results were obtained for 45 out of 92 cases with 46,XX, of which 2 (4.4%) showed XY signals. CONCLUSIONS: For accurate cytogenetic evaluation of spontaneous abortion materials, an additional technique such as FISH is required in order to confirm the cytogenetic results or to provide an estimate of the error rate in the analysis of miscarriages.     

FISH技术在检测自然流产绒毛组织非整倍体异常中的应用研究

目的:探讨运用荧光原位杂交(FISH)检测自然流产绒毛组织的临床价值,评价它与传统经典的核型分析方法的关系。方法:对157例孕早期自然流产的绒毛组织进行FISH检测,均采用16、22、13、21、18、X、Y号染色体荧光探针检测,判断染色体非整倍体异常情况。同时进行绒毛细胞培养染色体核型分析,作为对照诊断标准。结果:核型分析成功率为48.4%,FISH检测成功率为100%。核型分析成功的76例样本中,64例结果与核型分析结果相一致,以细胞遗传学作为诊断标准,诊断的符合率为84.2%。结论:FISH技术与传统的绒毛细胞培养染色体核型分析相比,过程迅速,方法简单,提高了诊断的成功率,但无法完全取代传统的染色体核型分析,应两者结合应用于临床。     

Use of PRINS for preconception screening of polar bodies for common aneuploidies

It has been shown that preconceptional screening for oocyte aneuploidies could help increase the pregnancy rate after in vitro fertilization (IVF), particularly in cases of advanced maternal age. The FISH (fluorescent in situ hybridization) technique is usually used to examine the first polar body (I-PB) for oocyte screening and so avoid fertilizing and transferring embryos from aneuploid oocytes. We have tested the feasibility of using another technique, the primed in situ (PRINS) reaction for this purpose. PRINS is a rapid, inexpensive method of labelling chromosomes. Chromosomes were labelled by in situ annealing with chromosome-specific oligonucleotide primers, followed by primer extension with labelled nucleotides using Taq DNA polymerase. A total of 183 PRINS reactions were performed with primers for chromosomes 13, 16, 18, 21 or X on 63 I-PBs removed from oocytes that failed to become fertilized during IVF. Each I-PB underwent three successive double-labelling reactions and intense signals were obtained in less than 40 min. Our data suggest that PRINS may be a useful alternative or a complement to FISH for detecting the main aneuploidies in all oocytes obtained after follicular puncture.     

Detection of chromosome abnormalities by quantitative fluorescent PCR in ectopic pregnancies

OBJECTIVE: To evaluate the potential value of quantitative fluorescent polymerase chain reaction (QF-PCR) in the detection of chromosome abnormalities in ectopic pregnancies. METHODS: Seventy chorionic villi samples of ectopic pregnancies were studied by QF-PCR. Primers for chromosomes 16, 21, X and Y in chorionic villi were evaluated. Fluorescence in situ hybridization (FISH) was performed when results of QF-PCR showed aneuploidy, in case of unexplicable QF-PCR peaks, and in 10 cases with normal QF-PCR results. RESULTS: QF-PCR produced a result for chromosomes X and Y in 66 cases (94%), for chromosome 16 in 62 cases (89%) and for chromosome 21 in 55 cases (79%). Overall, QF-PCR produced a result for the chromosomes tested in 54 ectopic pregnancy cases (77%). Fifty-two of these results were normal disomic (96%) and two were abnormal, one trisomy 16 (2%) and one triploidy (2%). In 16 cases (23%) no definite QF-PCR results could be obtained for all chromosomes, 11 due to amplification failure, and 5 due to unexplicable QF-PCR peaks. In 10 cases with normal QF-PCR results, disomy was confirmed by FISH. The trisomy 16 was also confirmed by FISH. Furthermore, a result was obtained with FISH in 5 of the cases without definite QF-PCR results. CONCLUSION: Although QF-PCR can establish the chromosomal status in ectopic pregnancies for chromosomes 16, 21, X and Y in the majority of cases, the technical failure rate is still considerable and does not improve results when compared to cytogenetic techniques.     

Fluorescence in situ hybridization (FISH) for rapid detection of aneuploidy: experience in 911 prenatal cases

Fluorescence in situ hybridization (FISH) was performed with probes specific for chromosomes 13, 18, 21, X and Y on 911 of 11123 (8.2%) amniotic fluid samples submitted to the present authors' laboratory for cytogenetic analysis over an 8-year period. Altogether 3516 hybridizations were performed with an interpretable FISH result on all chromosomes requested in 884/911 (97%) of cases. An uninformative FISH result occurred in 44 hybridizations among 27 cases (3%). Of a total of 89 karyotypically proven cases with aneuploidy that might have been detected by FISH, the overall detection rate was 84%. An inconclusive or incomplete FISH result occurred in 9/89 (10%) of these proven aneuploid cases. In the remaining 80 informative proven aneuploid cases, correct detection of aneuploidy was accomplished in 75/80 (94%) of samples. A false-negative result occurred in the remaining 5/80 (6%) of such informative cases. Eighteen cases had karyotypically proven abnormalities that could not have been detected by the targeted FISH. Aside from these 18 cases, FISH allowed correct detection of normal disomy in 785/804 (98%) of such cases. An incomplete FISH result occurred in 18 normal disomic cases. There was a single possible 'false-positive' FISH result for chromosome 21. Interphase FISH analysis of uncultured amniotic fluid cells has been shown to be a useful laboratory tool for rapid fetal aneuploidy screening during pregnancy. As with all clinical laboratory diagnostic tests, incomplete or inconclusive results (or even interpretive errors) occur in a small percentage of cases. Nevertheless, FISH results accompanied by other data and by appropriate counseling provide clinicians and patients with valuable information for clinical decision-making surrounding family planning and pregnancy management.     

Fast multicolor primed in situ protocol for chromosome identification in isolated cells may be used for human oocytes and polar bodies

OBJECTIVE: To present and evaluate the use of a new ultra-fast multicolor primed in situ (PRINS) procedure for karyotyping human oocytes and first polar bodies. DESIGN: In situ chromosomal identification on isolated cells, using combinations of specific primers for chromosomes 1, 7, 9, 16, and 18 and fluorescent nucleotides. SETTING: Sixteen unfertilized oocytes were obtained from women participating in an IVF program. PATIENT(S): Five patients undergoing an IVF-ET. INTERVENTION(S): In vitro unfertilized oocytes were fixed on slides, and sequential PRINS reactions were performed on each preparation. MAIN OUTCOME MEASURE(S): Ultrarapid in situ identification of three or four chromosomes on oocyte and polar body chromosome spreads. RESULT(S): On the basis of the direct in situ mixing of the colors of fluorochromes (FITC, TRITC, Cascade Blue) that were incorporated in sequential PRINS reactions, this method allows rapid and efficient labeling of three or four individual chromosomes. Each PRINS reaction consists of a unique 4- to 6-minute step for both in situ annealing and elongation. The procedure can be combined with fluorescence in situ hybridization (FISH) reactions. CONCLUSION(S): By simplifying the multicolor PRINS procedure, this new protocol should facilitate the use and adaptation of PRINS to chromosome screening. This approach could be used in parallel or in combination with FISH for efficient aneuploidy assessment on isolated cells.     

Role of FISH on uncultured amniocytes for the diagnosis of aneuploidies in the presence of fetal anomalies

OBJECTIVE: To assess the accuracy of fluorescent in situ hybridization (FISH) on amniocytes in fetuses affected by structural malformations suggestive of chromosomal anomalies. METHODS: FISH of uncultured amniotic fluid cells and conventional cytogenetic analysis were performed on 48 pregnancies with ultrasonographic (US) evidence of fetal anomalies. The AneuVysion assay (Vysis) with specific probes for chromosomes 13, 18, 21, X and Y, was used. Amniotic fluid samples were obtained between the 14th and 34th weeks of gestation. RESULTS: In cases with a single abnormal US finding (n = 15), 5 aneuploidies were detected (1 case of trisomy 13 and 4 of trisomy 21). In the group with two or more malformations (n = 33) there were 15 aneuploidies (9 cases of trisomy 18, 2 of trisomy 21, 2 monosomy X, 1 trisomy 13, and 1 triploidy). In this group, conventional cytogenetic analysis revealed two additional chromosomal anomalies not detectable by FISH (1 trisomy 16 mosaic, and a terminal deletion 4p). No sex aneuploidies were observed. CONCLUSIONS: The lack of false-positive diagnosis in the FISH analysis in our sample prompts us to consider interphase FISH as a useful tool in pregnancies at high risk for chromosomal aneuploidies. When FISH analysis is normal, the overall risk of chromosomal abnormalities is significantly reduced. However, the finding of two chromosomal anomalies undetectable by AneuVysion assay confirms the need for conventional chromosome analysis to complement FISH results. Moreover, the results collected here, in agreement with those already reported in the literature, indicate that FISH analysis on uncultured amniocytes can play an important role in counselling and decision-making, especially in cases at risk for aneuploidies, such as those with structural abnormalities at US.     

Comparison between fluorescence in situ hybridization (FISH) and quantitative-fluorescent polymerase chain reaction (QF-PCR) for the detection of aneuploidies in single blastomeres

OBJECTIVES: The aim of our investigation was to compare the efficiencies of the fluorescence in situ hybridization (FISH) and the quantitative-fluorescent PCR (QF-PCR) methods for the detection of sexing and numerical chromosome disorders in single blastomeres collected from the same preimplantation human embryos. METHODS: FISH analysis was carried out on 145 blastomeres from the 79 surplus embryos with probes specific for chromosomes 13, 18, 21, X, and Y. QF-PCR was performed with each one or two of the primers specific for the same chromosomes on 151 blastomeres from the same embryos obtained from patients undergoing IVF treatment. RESULTS: Analyses were possible on 135 blastomeres (93%) by FISH and on 117 blastomeres (77%) by QF-PCR. Of 65 embryos, which could be analyzed by both methods, 20 embryos (31%) were diagnosed as abnormal. CONCLUSION: The present study shows that FISH tests are more accurate than QF-PCR assays for the detection of numerical chromosome disorders when performed on single blastomeres.     

Simultaneous Detection of Chromosomes X, Y, 13, 18, and 21 by Fluorescence In Situ Hybridization in Blastomeres Obtained from Preimplantation Embryos

Purpose. Simultaneous fluorescence in situ hybridization (FISH) was used in a preimplantation genetic diagnosis program to determine which embryos were normal for chromosomes X, Y, 13, 18, and 21. Methods: Single blastomeres were disrupted and attached to glass slides using acetic acid and ethanol. Using a ratio mixture of chromosome enumeration DNA probes in combination with locus-specific identifier DNA probes, FISH was performed for the identification of chromosomes X, Y, 13, 18, and 21. Results: Fourteen couples enrolled in IVF produced 134 embryos for biopsy. Blastomeres subjected to five-color FISH revealed that 22% of embryos were normal for chromosomes X, Y, 13, 18, and 21. In addition, 52% were abnormal and no results could be detected for 25%. Twelve couples underwent embryo transfer, two couples did not receive embryos due to lack of any normal embryos, and three couples became pregnant. Conclusions: The simultaneous detection of five-color FISH is a feasible method to detect aneuploidy in preimplantation embryos from women of advanced maternal age.     

Aneuploidy screening in direct chorionic villus samples by fluorescence in situ hybridisation: the use of commercial probes in a clinical setting

The results of screening for the common aneuploidies involving chromosomes 13, 18, 21, X and Y by florescent in-situ hybridisation (FISH) in direct preparations from 100 chorionic villus samples from pregnancies between 10 and 20 weeks' gestation are reported. Samples prepared using routine methods and analysed with commercially available probes, accurately detected 12 cases of fetal aneuploidy, all referred because of developmental abnormality. Three of the four cases where chromosome abnormality was detected in cultured villi but not by the direct fluorescence in situ hybridisation (FISH) assay, were due to confined placental mosaicism. No chromosomal anomalies were found in the 20 low risk cases where the referral reason was a familial single gene disorder. We conclude that the FISH assay with commercial probes may act as an accurate and less labour intensive alternative to direct chromosome analysis of chorionic villus samples. In cytogenetically low risk cases its use can obtain a result within the time needed for DNA analysis and avoid the need to set up cultures.