Abstract
Fluorescence in situ hybridization (FISH) and manual scanning is a widely used strategy for retrieving rare cellular events such as fetal cells in maternal blood. In order to determine the efficiency of these techniques in detection of rare cells, slides of XX cells with predefined numbers (1–10) of XY cells were prepared. Following FISH hybridization, the slides were scanned blindly for the presence of XY cells by different observers. The average detection efficiency was 84% (125/148). Evaluation of probe hybridization in the missed events showed that 9% (2/23) were not hybridized, 17% (4/23) were poorly hybridized, while the hybridization was adequate for the remaining 74% (17/23). In conclusion, manual scanning is a relatively efficient method to recover rare cellular events, but about 16% of the events are missed; therefore, the number of fetal cells per unit volume of maternal blood has probably been underestimated when using manual scanning.
Highlights
Detection of rare cellular events has enormous potential in both cancer [1,2,3] and prenatal diagnosis [4,5,6,7]
We found that the hybridization efficiency of the Y probe in 5,000 pure XY cells, processed by conventional fluorescence in situ hybridization (FISH), was 99.1% (4,955/5,000)
We evaluated the retrieval of rare cellular events by a manual scanning-based FISH method, using an approach, which is summarized in Figure 1 and Table 1
Summary
Detection of rare cellular events has enormous potential in both cancer [1,2,3] and prenatal diagnosis [4,5,6,7]. The presence of fetal cells in maternal circulation generates a great amount of interest as a source of genetic material for noninvasive and risk-free diagnosis of aneuploidies and single gene disorders [8]. Instead of cell-free fetal DNA (cffDNA) in maternal plasma, fetal cells in the maternal blood can be an alternative approach for the development of a noninvasive method for prenatal diagnosis that accurately detects chromosome anomalies for two major reasons: (1) to work with pure fetal DNA material, which will allow specific characterization of fetal genome and (2) to have the whole genome of the fetus and not just part of it. Manual scanning is a commonly used strategy for retrieving these rare fetal cells from maternal blood
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