FLUORESCENCE IN-SITU HYBRIDIZATION (FISH) AS A METHOD TO DETECT ANEUPLOID CELLS

Objectives: To test the sensitivity and specificity of various FISH pr obes for detecting male and aneuploid cells and to determine the perce ntage of fetal cells that must be present in a sample in order to use the probes for prenatal diagnosis. Methods: Adult human lymphocytes we re cultured and harvested, Twelve different proportions of male to fem ale cells and 5 different propertions of trisomy 21 cells and trisomy 18 cells in euploid cells were prepared for FISH, Alpha-satellite DYZ1 was applied to detect the male cells, Chromosome 21/Down syndrome cri tical region cosmid and D13Z1/D21Z1 alpha-satellite probes were applie d to detect trisomy 21 cells, The D18Z1 alpha-satellite probe was used to detect trisomy 18 cells, Results: DYZ1 detected male cells reliabl y in concentrations as low as 2%, Both D18Z1 and chromosome 21/Down sy ndrome critical region cosmid probes could detect aneuploid cells at r easonably achievable concentrations, However, the D13Z1/D21Z1 probe wa s not sensitive below concentrations of 50%, Conclusions: FISH is an a lternative technique for noninvasive prenatal diagnosis, The sensitivi ty and specificity of FISH probes may play a crucial role in the accur acy of prenatal diagnosis.