Evaluation of the Cepheid Xpert® BCR-ABL Monitor and Ultra assays used to identify and monitor the presence of the oncogenic p210 BCR::ABL1 mRNA transcript in chronic myeloid leukaemia patients

Abstract

Background: The Philadelphia chromosome, a reciprocal translocation between chromosomes 9 and 22, results in a fused BCR::ABL1 oncogene. This fusion gene is the underlying molecular basis for chronic myeloid leukaemia (CML). Diagnostic and molecular monitoring of the BCR::ABL1 messenger ribonucleic acid (mRNA) transcript is part of the standard of care, enabling clinicians to monitor the efficacy of tyrosine kinase inhibitors (TKI) and discern patient responses to TKI therapy. Thus, any BCR::ABL1 test must be accurate and sensitive, as test results inform clinical decision-making regarding treatment. 
Objective: This study aimed to evaluate the automated Cepheid Xpert^® BCR-ABL Monitor and the improved Xpert^® BCR-ABL Ultra assay in a South African population with CML.
Methods: A total of 20 CML patients were monitored by assaying consecutive routine diagnostic blood samples using the Xpert^® BCR-ABL Monitor and Ultra assays in parallel on the Cepheid GeneXpert^® system.
Results: High concordance was found between the two assays, with a concordance correlation coefficient of 0.96 (95% confidence
interval [CI]; p < 0.001). The Xpert^® BCR-ABL Ultra assay demonstrated higher sensitivity, with a 95% sensitivity rate. Furthermore, the differences between the assay results had clinical significance, as 20% of newly diagnosed patients and 50% of patients already receiving treatment had a different treatment response between assays.
Conclusion: The improved Xpert^® BCR-ABL Ultra assay exhibited greater sensitivity, consistent with Cepheid’s reported performance. Furthermore, the Xpert^® BCR-ABL Ultra assay was an accurate test for detecting the BCR::ABL1 transcript based on its high sensitivity and specificity percentages.