Comparing morphology, flow cytometry and molecular genetics in the assessment of minimal residual disease in children with B-acute lymphoblastic leukaemia (B-ALL)

ackground: Minimal residual disease (MRD) detection has been shown to be the best prognostic factor in B-acute lymphoblastic leukaemia (B-ALL). Multicolour flow cytometry (FCM) and specific molecular aberrations (MOL) are the classic techniques used to assess MRD. The former is faster and less costly. Aim: This study compares morphology and FCM to MOL in detecting MRD. Setting: The study was conducted at Inkosi Albert Luthuli Central Hospital (IALCH). Methods: A retrospective review of children with B-ALL managed at IALCH from January 2013 to January 2018 was conducted. Multicolour flow cytometry was performed using Euroflow® panels. Molecular aberrations looked at common cytogenetic markers. Presentation and post-induction morphology (May–Grunwald Giemsa stain), FCM and MOL data for MRD were analysed. Results: Eleven patients were excluded (6-demised, 5-incomplete records), leaving 64 to be analysed (54% female, median age 5 years). Five post-induction aspirates were unsuitable but the rest (92%) were in morphological remission. At diagnosis and post-induction, 62 (95%) and 61 (94%) children, respectively, had FCM performed. A positive MOL result was found in 39 (60%) patients. MOL turn-around times (TATs) averaged 14 days compared with those of FCM’s average of 3 days. MRD was found in 9 patients (FCM) and 7 patients (MOL). Of these patients, 4 had a good correlation between the two and 2 patients with negative FCM had positive MOL MRD post-induction. Conclusion: Morphology is insensitive in MRD assessment. FCM correlated well with molecular MRD and has the shortest turn-around time. FCM has major benefit in the 40% of patients with negative MOL. It can also be safely used to guide treatment escalation in those patients awaiting molecular results.