Flow cytometric DNA index and karyotype in childhood lymphoblastic leukemia

Flow cytometric DNA-index (DI(FCM)) and karyotype were analysed in 82 consecutive children with acute lymphoblastic leukemia (ALL) during a 10 year period. A statistically significant correlation existed between modal chromosome number and DI(FCM) (p = 0.009). DI(FCM) could reliably identify leukemias with >51 chromosomes, whereas only three out of 12 cases with modal chromosome numbers between 47-51 were classified as aneuploid by DI(FCM). In the pseudodiploid group only one out of 20 leukemias had a DI(FCM) > 1.0. Five leukemias with a diploid karyotype showed an aneuploid DI(FCM) and in three patients the flow cytometric measurement revealed biclonality undetected by karyotyping. During treatment aneuploid clones could be detected by DI(FCM) in a substantial number of cases where the cytogenetic analysis was normal, and the opposite was also demonstrated in one case. DI(FCM) gave prognostic information, showing that cases with a DI > 1.12 (corresponding to 51 chromosomes) had a superior outcome with treatment protocols today in use.