Flow Cytometry Based Residual Disease Monitoring in Haematolymphoid Neoplasm

Measurable residual disease (MRD) presents a significant challenge for detection due to its elusive nature beyond routine diagnostic methods. Advancements in diagnostic modalities, particularly flow cytometry (FCM) and molecular techniques like polymerase chain reaction (PCR), revolutionised MRD assessment in haematological neoplasms. MRD assessment has emerged as a vital prognostic tool, enabling informed treatment decisions by offering a window of opportunity for targeted interventions before clinical relapse. Currently, two primary methodologies—molecular techniques and multicolour flow cytometry (MFC)—are employed for MRD evaluation. Molecular techniques, including real-time quantitative PCR and next-generation sequencing, provide detailed genomic analysis, whereas MFC identifies residual neoplastic cells based on immunophenotypic abnormalities. Advancements in flow cytometry technology, coupled with standardised protocols like EuroFlow guidelines, have enhanced the reproducibility and comparability of MRD assessments across laboratories. Notably, MFC allows rapid acquisition and analysis of a large number of cells, facilitating the identification of rare abnormal cell populations. Common haematological neoplasms benefiting from routine MRD analysis include AML, B-ALL, T-ALL, CLL, and MM, each requiring tailored approaches and evaluation criteria. This chapter provides the principle, technical details, and interpretation of MRD in various haematological neoplasm, as practiced in today’s era.