Reverse Transcription with Random Pentadecamer Primers Improves the Detection Limit of a Quantitative PCR Assay for BCR-ABL Transcripts in Chronic Myeloid Leukemia: Implications for Defining Sensitivity in Minimal Residual Disease

BACKGROUND: Real-time quantitative reverse transcrip-tion PCR (RQ-PCR) assay for BCR-ABL is used to monitor treatment response in chronic myeloid leuke-mia (CML). BCR-ABL transcript levels decline over several years of imatinib treatment, and increasing numbers of patients have BCR-ABL transcripts at or below the limit of detection.More sensitive PCRmeth-ods are required to assess whether these patients have a long-term continuing decline in residual disease. METHODS: We used random pentadecamer (R15) primers for reverse transcription in RQ-PCR and com-pared the results with our establishedmethod that uses random hexamers. An increase in assay sensitivity would be detected as an increase in the number ofBCR-ABL transcripts