The TEL‐AML1 real‐time quantitative polymerase chain reaction (PCR) might replace the antigen receptor‐based genomic PCR in clinical minimal residual disease studies 
in children with acute lymphoblastic leukaemia

Prospective studies in children with B‐precursor acute lymphoblastic leukaemia (ALL) have shown that polymerase chain reaction (PCR)‐based detection of minimal residual disease (MRD) using immunoglobin (Ig) and T‐cell receptor (TCR) gene rearrangements as targets can be used to identify patients with a high relapse risk. The disadvantage of this approach is that for each patient preferably two different targets have to be identified. The t(12;21)(p13;q22) with the TEL‐AML1 fusion gene is present in approximately 25% of children with B‐precursor ALL. In these patients, sensitive reverse transcription (RT)‐PCR analysis of the TEL‐AML1 fusion transcript might be a more simple and less laborious alternative approach. However, it is unknown how stable the mRNA is and whether the number of transcripts per leukaemic cell remains constant during follow‐up. We investigated whether the MRD results obtained using RT‐PCR of TEL‐AML1 transcripts correlated with the clinically validated genomic PCR for Ig and TCR gene rearrangements. Therefore, we used real‐time quantitative (RQ)‐PCR analysis for both types of targets and assessed the MRD levels in 36 follow‐up bone marrow samples (obtained during the first 1·5 years after diagnosis) from 13 patients with B‐precursor ALL. In 34/36 bone marrow samples the Ig/TCR RQ‐PCR and TEL‐AML1 RQ‐PCR revealed equal levels of MRD and these results had a strong correlation (P