¹Hematopathology Laboratory, Department of Pathology, Karolinska Hospital, Stockholm, Sweden

²Division of Hematology, Department of Medicine, Karolinska Institutet at Karolinska Hospital, Stockholm, Sweden

³Childhood Cancer Research Unit, Astrid Lindgren's Child Hospital, Stockholm, Sweden

Correspondence to: A Porwit-MacDonald, Department of Pathology, Karolinska Hospital, SE-171 76 Stockholm, Sweden; Fax: +46-851775843

^aContributed equally to this study. MM was responsible for molecular analyses and EB for flow cytometry studies

^bOn leave from Department of Epidemiology, Institute of Mother and Child Health, Warsaw, Poland

^cPresent address: Department of Oncology, Karolinska Hospital, Stockholm, Sweden

The analysis of minimal residual disease (MRD) has assumed a growing role in the follow-up of patients with acute lymphoblastic leukemia (ALL). We have applied multiparameter flow cytometry (FC) with 'live-gate' analysis and allele-specific oligonucleotide (ASO)-PCR detecting leukemia-specific T cell receptor and gene rearrangements for MRD follow-up in 30 ALL patients. The comparison of results obtained in 89 follow-up samples from 23 patients showed significantly consistent results in 70 samples (78%); (P < 0.001). Bone marrow samples taken during the first phase of treatment (during or immediately after induction) showed a lower level of consistency when compared to samples taken during later phases of treatment (69% vs 85% consistent results, respectively). Some of the discrepant results were due to low cellularity of the samples obtained for FC and some due to the presence of PCR inhibitors. Of 29 patients evaluated at the end of the induction treatment, 18 (62%) had detectable levels of MRD and six of these patients suffered relapse. In all these patients MRD levels by FC increased preceding relapse. Our results suggest that FC offers a MRD detection tool that can be easily applied in clinical practice and is as informative as molecular methods. Leukemia (2001) 15, 716-727.

minimal residual disease (MRD); acute lymphoblastic leukemia; polymerase chain reaction (PCR); T cell receptor (TcR); flow cytometry