Quantitative Assessment of the BCR-ABL Transcript Using the Cepheid Xpert BCR-ABL Monitor Assay

Abstract

Abstract Context.—Chronic myelogenous leukemia (CML) and the assessment of the BCR-ABL transcript has become a new paradigm. Novel tyrosine kinase inhibitors as mainstream therapeutic options for the CML patient warrant routine quantification of the BCR-ABL transcript. The Xpert BCR-ABL Monitor assay is a nested reverse transcriptase polymerase chain reaction that greatly reduces technical time by using a single cartridge to isolate RNA and run a quantitative reverse transcriptase polymerase chain reaction. Objective.—To evaluate the Xpert BCR-ABL Monitor assay for quantitative assessment of the BCR-ABL transcript in CML patients. Design.—A standard curve of K-562 cells diluted in normal peripheral blood was used to test the sensitivity, linearity, and percent coefficient of variation of the assay. Specimen stability was tested by running standard curves immediately and after 24 hours or 96 hours of storage at 4°C. Specimens from normal controls, patients known to have CML, or patients suspected of having CML were also tested. Results.—The sensitivity of the assay was sufficient to detect 1 K-562 cell in 105 normal cells. The R2 of the standard curve was 0.98 and the percent coefficient of variation for each data point was 15% to 24%. Eleven of 14 patients with known CML on imatinib treatment tested positive for the BCR-ABL transcript, whereas 10 normal controls tested negative. Conclusions.—The Xpert BCR-ABL Monitor assay is a rapid, sensitive method for monitoring the presence of the BCR-ABL transcript in CML patients. The single-use cartridge minimizes hands-on technical time, minimizes the potential for contamination, and allows quantitative BCR-ABL testing to be performed in a random access fashion.