Comparison of autoradiography and DNA histograms in assessing S-phase cells from patients with myeloid leukemias.

The studies reported here were designed to determine whether DNA histogram analysis provided the same estimate for the percentage of cells in S-phase as does 3H-TdR labeling index (LI). For DNA histogram analysis high resolution flow cytometry was employed together with 3 different computer based methods for histogram analysis. When tissue culture cells were employed there was a good correlation (r = 0.89) between the estimates for the percentage of cells in S-phase by the LI and DNA histogram techniques. In contrast, when 1138 bone marrow or peripheral blood specimens obtained from leukemic patients were studied the correlation was poor. For example when 243 pretherapy bone marrow aspirate cells were studied by both methods the correlation was only 0.46. A direct comparison of the clinical relevance of the two methods for measuring S-phase cells when high dose cytosine arabinoside therapy was used to treat patients demonstrated that only LI measurements provided clinically useful information. In conclusion, DNA histogram analysis provides an inaccurate estimate of the percentage of cells in S-phase.