Svennevik, Elizabeth Clare; (1998) Development and evaluation of molecular cytogenetic techniques for use in clinical diagnostics. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The most frequent aneuploidies in newborns involve chromosomes 13, 18, 21, X and Y. Fluorescence in situ hybridisation on uncultured amniocytes would diagnose aneuploidies more rapidly than conventional karyotype analysis but the sensibvity and specificity of FISH on these cells depends on the probes used and the different cell preparation methods. These parameters have been investigated and following an encouraging pilot study a prenatal diagnostic FISH test on uncultured amniocytes has been introduced into routine practice in the clinical cytogenetics laboratory at University College London Hospital. There were no false positive or false negative results in the preliminary series of 155 samples to which the probe sets for chromosomes 13, 21 and 18, X and Y were applied but it was concluded that there is a risk of misdiagnosis through maternal cell contamination in grossly blood stained samples. The major disadvantage of the technique is the risk of overlooking other chromosome abnormalities which may be as serious as the most frequently observed aneuploidies. It is therefore considered that FISH on uncultured amniocytes should be used as an adjunct to classical cytogenetics.. Interphase FISH has been attempted on blood smears for rapid diagnosis of suspected aneuploidy, with limited success, and more convincingly on cells from products of conception and direct preparations from chorionic villus samples. Comparative Genomic Hybridisation was originally developed for the rapid and comprehensive assessment of malignant samples for genetic imbalance. The possibility of utilising CGH in routine cytogenetics has been investigated and aneuploidies have been detected using this approach. However, the technique is laborious and the results from the present study suggest that furthur technical development is required before CGH can be considered applicable for routine aberration screening.

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