A new R-banding technique in clinical cytogenetics.

Currently, standard methods of chromosome banding detect an abnormality in some 10%--15% of all patients referred for a cytogenetic study. Higher resolution by the study of the less contracted chromosomes with or without cell synchronization techniques may yield higher frequencies in the future. On the other hand, use of more complicated methodology adds to the time and expense needed for the study. The method of 5' bromodeoxyuridine pretreatment of cells in culture is commonly used to study the replication behavior of X chromosomes, and is known to demonstrate R bands along the other chromosomes. We have modified this technique with the addition of a cell synchronization step and evaluated several variables that are of importance in a clinical service laboratory setting. The method offers a simple way to obtain quality R-banded karyotypes. The advantages and limitations, based on our study of 120 consecutive cultures, are described.