Utility and limitations of chromosome banding in pre- and postnatal service cytogenetics.

This report analyzes detection rates of chromosome aberrations as a function of stainig technique. Of 1,717 peripheral lymphocyte cultures processed by a midsize service cytogenetics laboratory, 23 chromosomal aberrations (1.3%) would not have been detected without the use of either R-banding or G-banding. These 23 cases comprise 21 of 64 non-Robertsonian structural autosomal changes and two of 68 gonosomal aberrations. In contrast, in 1,634 amniotic fluid cell cultures only one balanced rearrangement (0.06% of all cases) would not have been detected without banding. Combined with incidence rates from newborn cytogenetic screenings, these figures suggest that among 10,000 prenatal diagnoses for advanced maternal age, at most one chromosomally unbalanced fetus would be missed if banding were not routinely applied. Because of savings in time and possible automation, it is estimated that discretionary rather than routine use of chromosome banding in prenatal cytogenetics would allow for detection of at least twice as many age-related aneuploidies. In view of sharply rising demand for prenatal cytogenetic services, a discretionary approach might therefore assure a more equitable distribution of limited cytogenetic resources.