Automatic Scanning of Interphase FISH for Prenatal Diagnosis in Uncultured Amniocytes

An Overview on Prenatal Screening for Chromosomal Aberrations

This article is a review of current and emerging methods used for prenatal detection of chromosomal aneuploidies. Chromosomal anomalies in the developing fetus can occur in any pregnancy and lead to death prior to or shortly after birth or to costly lifelong disabilities. Early detection of fetal chromosomal aneuploidies, an atypical number of certain chromosomes, can help parents evaluate their pregnancy options. Current diagnostic methods include maternal serum sampling or nuchal translucency testing, which are minimally invasive diagnostics, but lack sensitivity and specificity. The gold standard, karyotyping, requires amniocentesis or chorionic villus sampling, which are highly invasive and can cause abortions. In addition, many of these methods have long turnaround times, which can cause anxiety in mothers. Next-generation sequencing of fetal DNA in maternal blood enables minimally invasive, sensitive, and reasonably rapid analysis of fetal chromosomal anomalies and can be of clinical utility to parents. This review covers traditional methods and next-generation sequencing techniques for diagnosing aneuploidies in terms of clinical utility, technological characteristics, and market potential.

FISH and tips: a large scale analysis of automated versus manual scoring for sperm aneuploidy detection

Background

Approximately 1% of the spermatozoa found in ejaculate of healthy men are aneuploid and this rate increases in the population of subfertile and infertile men. Moreover, fertilization with these aneuploid sperm can lead to impaired embryo development. Fluorescent In Situ Hybridization (FISH) is the common cytogenetic tool used for aneuploidy screening on sperm. However, it is a time-consuming technique and cytogenetic or in vitro fertilization laboratories cannot routinely use it and face the increasing demand of such analyses before Assisted Reproductive Techniques (ART). As automation can be a clue for routine practice, this study compares manual and automated scoring of sperm aneuploidy rates using a Metafer Metasystems® device. The results obtained also contribute to global data about FISH on sperm cells.

Methods

We recruited 100 men addressed for sperm cryopreservation. They all signed an informed consent to participate in the study. 29 men were donors or consulted before vasectomy (control group) and 71 were suffering of Hodgkin’s disease or non Hodgkin lymphoma (patient group). One semen sample was collected for each patient, analyzed according to WHO criteria and prepared for a triple-color FISH using centromeric probes for chromosomes 18, X and Y. Automated scoring was performed using a Metafer Metasystems® device.

Results

507,019 cells were scored. We found a strong concordance between the automated and the manual reading (d < 0.01 in Bland-Altman test). We also did not find a statistically significant difference between the automated and the manual reading using Wilcoxon test for total aneuploidy rate (p = 0.06), sex chromosomes disomy (p = 0.33), chromosome 18 disomy (p = 0.39) and diploidy (p = 0.21). Cumulative rate of total aneuploidy was 0.78% ± 0.212% for patient group and 0.54% ± 0.15 for control group and among this, sex chromosome XY disomy rate was of 0.54% for patient group and 0.27% for control group.

Conclusion

This study validates the automated reading for FISH on sperm with a Metafer Metasystems® device and allows its use in a laboratory routine.

State-of-the-art FISHing: automated analysis of cytogenetic aberrations in interphase nuclei

Interphase fluorescence in situ hybridization (i-FISH) is a powerful tool for visualizing various molecular targets in non-dividing cells. Manual scoring of i-FISH signals is a labor intensive, time-consuming, and error-prone process liable to subjective interpretation. Automated evaluation of signal patterns provides the opportunity to overcome these difficulties. The first report on automated i-FISH analysis has been published 20 years ago and since then several applications have been introduced in the fields of oncology, and prenatal and fertility screening. In this article, we provide an insight into the automated i-FISH analysis including its course, brief history, clinical applications, and advantages and challenges. The lack of guidelines for describing new automated i-FISH methods hampers the precise comparison of performance of various applications published, thus, we make a proposal for a panel of parameters essential to introduce and standardize new applications and reproduce previously described technologies.

Automated four-color interphase fluorescence in situ hybridization approach for the simultaneous detection of specific aneuploidies of diagnostic and prognostic significance in high hyperdiploid acute lymphoblastic leukemia

In high hyperdiploid acute lymphoblastic leukemia (ALL), the concurrence of specific trisomies confers a more favorable outcome than hyperdiploidy alone. Interphase fluorescence in situ hybridization (FISH) complements conventional cytogenetics (CC) through its sensitivity and ability to detect chromosome aberrations in nondividing cells. To overcome the limits of manual I-FISH, we developed an automated four-color I-FISH approach and assessed its ability to detect concurrent aneuploidies in ALL. I-FISH was performed using centromeric probes for chromosomes 4, 6, 10, and 17. Parameters established for nucleus selection and signal detection were evaluated. Cutoff values were determined. Combinations of aneuploidies were considered relevant when each aneuploidy was individually significant. Results obtained in 10 patient samples were compared with those obtained with CC. Various combinations of aneuploidies were identified. All clones detected by CC were observed also by I-FISH, and I-FISH revealed numerous additional abnormal clones in all patients, ranging from < or =1% to 31.6% of cells analyzed. We conclude that four-color automated I-FISH permits the identification of concurrent aneuploidies of potential prognostic significance. Large numbers of cells can be analyzed rapidly. The large number of nuclei scored revealed a high level of chromosome variability both at diagnosis and relapse, the prognostic significance of which is of considerable clinical interest and merits further evaluation.

Automated scoring of multiprobe FISH in human spermatozoa

In the case of chromosomal aneuploidy in sperm wherein the incident rate is low and a large number of cells require scoring, automated methods that rely on computer software to segment and to count fluorescence signals are particularly necessary due to countless hours spent in reading slides and to the potential for interoperator differences. The purpose of this pilot experiment was to determine whether there were significant differences in the estimates of disomy frequency produced by automated versus manual scoring of signals for chromosome X, Y, and 18 in human sperm. The frequency of X18, Y18, XX18, YY18, and XY18 were determined in four separate normozoospermic samples. Slides were hybridized using a standard sperm FISH protocol for centromere-specific probes. Between 500 and 564, DAPI positive nuclei were captured from each sample and scored using the automated system, and the same slides were scored by a trained cytogeneticist, who was blind to the purpose of the study and the automated system results. None of the estimated frequencies was significantly different between manual and automated methods, regardless of whether individual slides or pooled results across all samples were compared. To our knowledge, this is the first report examining the validity of automated cell scoring in human spermatozoa. The results from this pilot exploration of sperm FISH suggest the comparability between automated and manual methods for estimating sex chromosome disomy and provide evidence that automated laser scanning of multiprobe sperm FISH should be explored further.

Development of a non-human primate sperm aneuploidy assay tested in the rhesus macaque (Macaca mulatta)

Numerical chromosome aberrations in germ cells are important factors contributing to abnormal reproductive outcomes. Fluorescence in situ hybridization onto spermatozoa (sperm-FISH) has allowed the study of the influence of a wide range of biological factors and chemical exposure on aneuploidy incidences in human sperm as well as in mouse and rat animal models. The assay presented here extends the applicability of the sperm-FISH method to non-human primates and was tested in the prevalent model species, the rhesus macaque. The assay provides probes for macaque chromosomes 17, 18, 19, 20, X and Y, the homologues of human chromosomes 13, 18, 19, 16, X and Y, respectively. The analysis of 11 000 spermatozoa each from five individuals revealed spontaneous sex chromosomal disomy frequencies (X: 0.08%; Y: 0.09%) and an average autosomal disomy frequency (0.03%) coinciding with some of the lowest incidences scored in human studies. The non-human primate sperm-FISH assay provides a fast and efficient tool complementing the available analysis methods in non-human primate exposure studies. Since the assay employs large locus-specific FISH probes representing evolutionary conserved DNA sequences, it can be expected that the assay is also applicable to other cercopithecoid and hominoid non-human primate species.

Automated Duet spot counting system and manual technologist scoring using dual-fusion fluorescence in situ hybridization (D-FISH) strategy: comparison and application to FISH minimal residual disease testing in patients with chronic myeloid leukemia

The automated BioView Duet system was compared with manual technologist scoring (MTS) using a BCR/ABL dual-fusion FISH (D-FISH) probe strategy for chronic myeloid leukemia (CML) specimens. In the first study, 500 nuclei were evaluated for 10 distinct signal patterns in various abnormal cell percentages from each of 89 specimens. The Duet system correctly identified all 27 normal specimens and the abnormal signal pattern of all 63 abnormal specimens. The percentage of abnormal nuclei detected was also concordant, with an average difference between MTS and the Duet system of only 2.7%. However, achievement of accurate quantitative results required reclassification by a technologist for nearly 50% of nuclei per specimen. Next, the Duet system was used to evaluate BCR/ABL D-FISH for FISH minimal residual disease (MRD) detection in CML patients. Up to 6,000 nuclei were evaluated for four signal pattern categories for each of 60 CML MRD samples. Excluding four abnormal specimens with insufficient samples, the Duet system correctly identified all of the abnormal specimens and identified four additional abnormal specimens previously diagnosed as normal by MTS. The technologist time required for evaluation and reclassification of the Duet system data for the FISH MRD samples averaged only 1 minute per case, saving significant technologist effort. We conclude that the Duet system appears to be more sensitive and cost-effective than MTS for CML FISH MRD testing.

Fluorescent in situ hybridization (FISH) in bone marrow and peripheral blood of leukemia patients: implications for occupational surveillance

Although there has been a rapid rise in the application of fluorescent in situ hybridization (FISH) analysis of bone marrow tissue for the staging and prognosis determination of hematopoietic malignacies such as the chronic and acute leukemias, it's application as a surveillance tool for leukemogen exposed high risk occupational cohorts is understandably limited by the invasiveness of sample collection. While some small occupational studies have been performed using FISH in peripheral blood with promising results, some of the basic assumptions made in utilizing the FISH technique have not been fully explored. These include selection of the correct hematopoietic cell to assay (myeloid or lymphoid); selection of appropriate chromosomal markers and the sensitivity of peripheral blood FISH in detecting unbalanced genomic abnormalities. In this study, we performed a pilot 'validation' exercise utilizing the FISH technique and standard metaphase cytogenetics, comparing results in tandem pairs of peripheral blood with bone marrow cells, where clonal abnormalities arise. Samples were taken from patients with known chromosomal lesions associated with active leukemia. We carefully chose markers most frequently associated with leukemogen-inducing DNA damage and probes that have been utilized successfully in clinical practice. Ten de novo or therapy-related acute myeloid leukemia (t-AML) patients underwent bone marrow cell karyotyping and fluorescent in situ hybridization (FISH) analysis. Parallel peripheral blood samples were concommitently drawn and evaluated with FISH using the same probes. In six of eight paired samples treated with a 3-day phytohemagglutinin (PHA) stimulation, typically used to assay lymphocytes and their progenitors, we detected abnormal clones. In one of the two remaining cases, we identified an abnormal clone in both bone marrow and PHA-stimulated peripheral blood, although at a level in the peripheral blood sample that would typically be reported as "non-diagnostic" for clinical purposes. These results suggest that use of FISH in PHA stimulated peripheral blood samples with probes commonly employed in t-AML evaluations (chromosomes 5q, 7q, 8, 11q) to detect cytogenetic abnormalities in peripheral blood represents a potentially promising though as yet, under-utilized approach for the occupational surveillance of workers exposed to leukemogens, especially if it could be linked to automated high-throughput assays for increased sensitivity.

Fully automated FISH examination of amniotic fluid cells

OBJECTIVE

Fluorescence in situ hybridization (FISH) analysis has become a valuable adjunct in cytogenetics, providing a rapid screen for common chromosome abnormalities that is particularly helpful in prenatal diagnosis. FISH analysis using standard microscopy is expensive and labor intensive, requiring both a high skill level and subjective signal interpretation. A reliable fully automated system for FISH analysis could improve laboratory efficiency and potentially reduce errors and costs.

METHODS

The efficacy of an automated system was compared to standard manual FISH analysis. Two sets of slides were generated from each of 152 amniotic fluid samples. Following hybridization with a standard panel of five chromosome FISH probes, one set of slides was evaluated using manual microscopy. The other set was evaluated using an automated microscopy system.

RESULTS

A diagnostic outcome was obtained for all 152 samples using manual microscopy and for 146 of 152 (96%) samples using automated microscopy. Three cases of aneuploidy were detected. For those samples for which a diagnostic outcome was determined by both manual and automated microscopy, 100% concordance was observed. All FISH analysis results were confirmed by karyotype.

CONCLUSION

These data suggest that an automated microscopy system is capable of providing accurate and rapid enumeration of FISH signals in amniocytes.