An assessment of the metaphase finding capability of the Cytoscan 110.

The Cytoscan 110 metaphase finder has been tested with cultures of human peripheral blood lymphocytes prior to its introduction into routine use for the analysis of radiation-induced chromosomal damage. Cells of varying quality and density of distribution on slides, stained with orcein or Giemsa, were examined by the same technician using the Cytoscan and a conventional microscope. The Cytoscan was able to locate rapidly (less than 2 min) virtually all metaphases known to be present and with an acceptably low rate of false positives. The presence of mixtures of FPG-stained first- and second-division spreads did not reduce its efficiency in metaphase finding. The instrument automatically divides the objects that it locates into 4 quality ranks and this was very effective in separating good metaphases, suitable for high-magnification scoring, from unscorable spreads and debris. With cultures of X-irradiated blood it was shown that the criteria by which the Cytoscan locates metaphases and ranks their appearance do not introduce bias in the yields of dicentric and other unstable chromosome-type aberrations.