Thue Bryndorf

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Albert Ruda Gonzalez

Universitat de Girona

Dr.Mahmoud Lotfy

Minufiya University

Andrea Colorio

Università degli Studi di Milano-Bicocca

Dominic D'Agostino

University of South Florida

David Vago

Vanderbilt University

David Sharp

Imperial College London

Nicolas A Karakatsanis

Weill Cornell Medicine

Sabbir Shuvo

University of Manitoba

Scott Wilson

Sewanee: The University of the South

Andrea Chiba

University of California, San Diego

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New rapid test for prenatal detection of trisomy 21 (Down's syndrome): preliminary report

British Medical Journal, 1992

OBJECTIVE--To devise and evaluate a rapid screening method for detecting trisomy 21 (Down's s... more OBJECTIVE--To devise and evaluate a rapid screening method for detecting trisomy 21 (Down's syndrome) in samples of uncultured amniotic fluid cells. DESIGN--Non-radioactive in situ hybridisation with HY128, a 500,000 base pair yeast artificial chromosome probe specific for chromosome 21. Blinded study of 12 karyotypically normal amniotic fluid samples and eight samples trisomic for chromosome 21. SETTING--Cytogenetic and obstetric services at

Image analysis in comparative genomic hybridization

Cytometry, 1995

Comparative genomic hybridization (CGH) is a new technique by which genomic imbalances can be det... more Comparative genomic hybridization (CGH) is a new technique by which genomic imbalances can be detected by combining in situ suppression hybridization of whole genomic DNA and image analysis. We have developed software for rapid, quantitative CGH image analysis by a modification and extension of the standard software used for routine karyotyping of G-banded metaphase spreads in the Magiscan chromosome analysis system. The DAPI-counterstained metaphase spread is karyotyped interactively. Corrections for image shifts between the DAPI, FITC, and TRITC images are done manually by moving the three images relative to each other. The fluorescence background is subtracted. A mean filter is applied to smooth the FITC and TRITC images before the fluorescence ratio between the individual FITC- and TRITC-stained chromosomes is computed pixel by pixel inside the area of the chromosomes determined by the DAPI boundaries. Fluorescence intensity ratio profiles are generated, and peaks and valleys indicating possible gains and losses of test DNA are marked if they exceed ratios below 0.75 and above 1.25. By combining the analysis of several metaphase spreads, consistent findings of gains and losses in all or almost all spreads indicate chromosomal imbalance. Chromosomal imbalances are detected either by visual inspection of fluorescence ratio (FR) profiles or by a statistical approach that compares FR measurements of the individual case with measurements of normal chromosomes. The complete analysis of one metaphase can be carried out in approximately 10 minutes.

Prenatal aneuploidy detection in interphase cells by fluorescencein situ hybridization (Fish)

Prenatal Diagnosis, 1994

FISH is a quick, inexpensive, accurate, sensitive and relatively specific method for aneuploidy d... more FISH is a quick, inexpensive, accurate, sensitive and relatively specific method for aneuploidy detection in samples of uncultured chorionic villus cells and amniotic fluid cells. FISH allows detection of the autosomal trisomies 13, 18 and 21 and X and Y abnormalities and any other chromosome abnormality for which a specific probe is available. The detection rate of these abnormalities is high in informative samples which have a concordance of >99.5% with cytogenetic results. A relatively high number of abnormal cases are found in uninformative samples. However, such samples should be regarded as samples to be investigated further. Clinical experience with the use of FISH for prenatal diagnosis is now beyond 10,000 cases; a number of clinical protocols and smaller trials have also been carried out, resulting in 90% of attempted analyses giving informative results with a high detection rate and extraordinarily low false-positive and false-negative rates Unsolved problems remain, such as occasional technical failures, admixtures of maternal blood and up to 20% uninformative scoring results, especially for abnormal specimens. FISH is at present used as an adjunct to classical cytogenetic analysis. However, this should not be interpreted as meaning that FISH could not be used as a methodology in its own right. If FISH were to be considered a diagnostic test then this might be the case, due to the risk of false-negative and false-positive results and the fact that FISH does not allow a diagnosis of certain structural abnormalities. If, on the other hand, FISH is considered a screening test, which means that in all abnormal (or indeterminate) cases, classical cytogenetic analysis would follow the abnormal screening test, the accuracy which is potentially higher than for other screening methods, for example in cases of trisomy 21, justifies FISH as a prenatal screening test in its own right.

Thue Bryndorf

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