IgH gene rearrangement by PCR as an adjunct to flow cytometric analysis for the detection of minimal residual disease in patients with B lymphoblastic leukemia

To examine the benefits of performing flow cytometry and PCR for IGH gene rearrangement in parallel for the detection of minimal residual disease (MRD) in patients with B lymphoblastic leukemia. A flow cytometric assay for MRD and PCR-based assay for IGH gene rearrangement were performed, concurrently, on bone marrow evaluations from patients with a new or previous diagnosis of B-ALL from Oct 1, 2016, to Mar 25, 2019. The results were compared by the kappa (K) statistic. A total of 119 cases had concurrent flow cytometry and PCR for monoclonal IGH gene rearrangement performed. The overall percent agreement was 84% (K = 0.739, 95% CI 0.62–0.86). Concordant positive follow-up cases did not contain a significantly higher percentage of B cells versus flow cytometry-positive, PCR-negative follow-up cases (0.41% vs 1.69% p = 0.22). In one patient who received chimeric antigen receptor T cell therapy, MRD was detectable only by PCR. The IGH gene rearrangement assay, in conjunction with flow cytometry, has clinical utility in the diagnosis of MRD in patients with B-ALL. PCR for IGH gene rearrangement may improve the monitoring of patients with tumor phenotypes challenging to detect by flow cytometry.