Detection of residual BCR/ABL transcripts in chronic myeloid leukaemia patients in complete remission using the polymerase chain reaction and nested primers.

We sought evidence of BCR/ABL transcripts in the peripheral blood of nine CML patients in complete clinical and cytogenetic remission after treatment by bone marrow transplantation (BMT) or interferon and in one patient who entered spontaneous remission. Six patients were investigated at different times during their follow-up. We compared results obtained with the polymerase chain reaction (PCR) using (a) a single-stage PCR comprising 30 cycles of amplification with selected oligomers, and (b) a two-stage procedure in which the reaction product from the first stage was subjected to a further 30 cycles with nested amplimers. Special care was taken to assess contamination, including for each patient simultaneous co-extraction of a negative control. Blood cells from all patients showed no evidence of BCR/ABL transcripts in the one-stage PCR but 9/17 specimens were positive in the two-stage procedure. Patients in complete remission for a long time (greater than 2 years) appeared negative. These results serve in part to explain the discordant findings reported in other studies and emphasize the importance of carefully selecting the technical conditions most likely to give results that are prognostically relevant for individual patients.