Routine use of methods for improved G-band resolution in a population of patients with malformations and developmental delay.

We report on an 11-year experience in which cell culture synchronization and other methods for improving cytogenetic detail were used to study 2,245 patients presenting with malformations and (usually) developmental delay. Not including patients presenting with one of the so-called "contiguous gene syndromes," 30 patients (1.1% of the study population) were found to have karyotypes characterized by structural alterations that were either subtle enough to be judged undetectable in standard metaphase preparations or subtle enough to have escaped detection in previous banded studies. Analysis of the detail available for 6 chromosome pairs suggests that the average banding detail available for these analyses fell short of that considered to be "high-resolution" but was, nevertheless, more than would have been expected from standard metaphase preparations.