Evaluation of diagnostic sensitivity and specificity of 10-colour flow cytometry testing for disease monitoring/detection on the Navios/NaviosEx, Kaluza C platform, in comparison to RQ-PCR testing

Abstract

Background Measurable residual disease (MRD) analysis is critical in acute lymphoblastic leukaemia (ALL) management protocols. Real-time quantitative polymerase chain reaction (RQ-PCR) is the accepted gold standard in MRD testing. Multiparameter flow cytometry has emerged as a comparative testing modality. We evaluated the concordance of our centre’s 10-colour flow cytometry (Navios/NaviosEx) with RQ-PCR (ABI 7500 Fast Real Time PCR) for MRD detection. Aim To investigate the concordance of flow cytometry MRD results versus RQ-PCR; and immunoglobulin heavy chain (IgH) rearrangement PCR versus RQ-PCR. Setting The National Health Laboratory Services Flow Cytometry and Somatic Cell Genetics Units at the Charlotte Maxeke Johannesburg Academic Hospital. Methods Flow cytometry results between March 2020 and June 2023 were compared to RQ-PCR results in follow-up samples from patients with a diagnosis of B-cell ALL, bearing one of the following recurrent genetic lesions; t(1;19), t(12;21) or t(9;22). Results A total of 74 bone marrow aspirate samples were eligible for inclusion. The flow cytometry assay showed a low sensitivity (13%) but a high specificity (98%) when compared to RQ-PCR. The positive and negative predictive values were 75% and 71%, below the acceptable levels of 80% and 90% respectively. The IgH assay showed better sensitivity (43%) and a positive predictive value of 91%. 3 Conclusion The flow cytometry assay at our center exhibited significantly lower sensitivity compared to PCR-based methods for the detection of MRD in follow-up cases of B-ALL. Among the PCR techniques, RQ-PCR demonstrated superior sensitivity for MRD detection.