DNA-Analysis by Flow-Cytometry of up to Nine Year Old Methanol/Acetic Acid Fixed Samples of Childhood Acute Lymphoblastic Leukemia (ALL)

According to cytogenetic abnormalities, several prognostically important groups can be distinguished in childhood acute lymphoblastic leukemia (ALL). However, owing to the technical difficulties in obtaining a sufficient and representative number of analysable metaphases, additional techniques are required for substitution or for confirmation of cytogenetic findings. One of these alternatives using a fast and technically simple method is the determination of gross quantitative deviations of the DNA content by flow-cytometry. Although the best results are obtained with fresh material, in many instances the analysis of material previously used for cytogenetic analysis may be of interest. We have therefore adopted a DAPI-staining technique for flow-cytometric analysis of methanol/acetic acid fixed samples. We have used this method to measure 44 methanol/acetic acid fixed samples which had been stored in — 20 °C for a period ranging from several months to nine years. Cytogenetically the samples comprised hypo-, pseudo- and hyperdiploid cases as well as some in which no results could be obtained. We detected 29 abnormal samples with 34 aneuploid clones. Six of them were hypo- (DNA-index (DI) 0.57–0.82) and 28 hyperdiploid (DI 1.04–1.92). Four samples contained a hypo- as well as a hyperdiploid clone, and one case two hyperdiploid clones. Twenty out of 28 hyperdiploid clones were also detected with cytogenetic analysis, whereas no hypo-diploid clones were found. The variant of coefficiency (CV) of the measurements ranged from 1,40 to 4,20% (median 2.8 ± 0.62%).