The aim of our study was to evaluate the usefulness of the PCR technique as a means for the detection of monoclonality at diagnosis and during follow-up of ALL of childhood. Patient group (A) 23 ALL patients diagnosed in 1996 (22 B-cell ALL, 1 T-cell ALL) were studied at diagnosis and post-induction; 8/23 were also studied during the consolidation phase. (B) 30 ALL patients not studied at diagnosis, were analyzed at various times during consolidation, maintenance or at clinical relapse of the disease.

Materials-Methods: High molecular weight DNA was isolated from bone marrow samples (obtained for routine diagnostic and follow-up purposes) with proteinase K digestion and phenol/chloroform extraction. PCR was carried out on one microgram of genomic DNA using as primers oligonucleotides specific for the variable and the joining region genes of the immunoglobulin heavy and k-light chain genes (IgH, IgK) and the T-cell receptor γ and δ chain genes (TCRγ, TCRδ), either in an one-round (diagnostic samples) or in a semi-nested approach (minimal residual disease, MRD samples).Table

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Conclusion: (i) At diagnosis of childhood ALL it may be helpful to seek as many molecular markers of monoclonality as possible. (ii) The results in group B illustrate the limitations of the approach when molecular analysis is not undertaken at diagnosis. (iii) Due both to technical (mainly primer-related) and biologic reasons (oligoclonality at diagnosis, clonal evolution), the detection of MRD in childhood ALL by conventional PCR approaches presents many problems, is of limited specificity and sensitivity and should be replaced by an alternative patient-based (clone-specific) approach.