Methods of processing marrow samples may affect the frequency of detectable aneuploid cells

Karyotypes were analyzed from 14 patients with various myeloproliferative disorders who had marrow samples processed directly and cultured in various ways. Eleven patients had acute nonlymphocytic leukemia (ANLL) (seven patients) or a dysmyelopoietic syndrome (four patients). All of these patients were known to have an abnormal karyotype, and in each case, two samples of a bone marrow aspirate were available: one processed directly and another cultured for 24 hr. Five of the 11 patients had essentially the same proportion of abnormal cells in the direct and 24-hr samples; in five other patients, the percentage of aneuploid cells in the sample cultured for 24 hr was higher than that in the direct preparation. A higher percentage of aneuploid cells was observed in the direct preparation in only one case. In three other cases of ANLL, a marrow aspirate was cultured with methotrexate in addition to samples processed directly and after 24-hr culture; only two of these had an abnormal clone in any sample. The results of karyotype analysis differed in these two patients. The proportion of aneuploid cells was substantially higher in the methotrexate culture than in the 24-hr culture in one patient; in the other patient, the 24-hr culture contained aneuploid cells, whereas the methotrexate culture showed none. Three of the 13 aneuploid patients would have been incorrectly classified as being karyotypically normal on the basis of the initial analysis of the direct preparation, since only a single abnormal cell was detected in each case. The karyotypic pattern in untreated patients with ANLL has prognostic significance; therefore, the method of processing marrow aspirates may substantially influence the degree of correlation between the karyotype and survival reported by different laboratories.