The ALLgorithMM: How to define the hemodilution of bone marrow samples in lymphoproliferative diseases

Abstract

IntroductionMinimal residual disease (MRD) is commonly assessed in bone marrow (BM) aspirate. However, sample quality can impair the MRD measurement, leading to underestimated residual cells and to false negative results. To define a reliable and reproducible method for the assessment of BM hemodilution, several flow cytometry (FC) strategies for hemodilution evaluation have been compared.MethodsFor each BM sample, cells populations with a well-known distribution in BM and peripheral blood - e.g., mast cells (MC), immature (IG) and mature granulocytes (N) – have been studied by FC and quantified alongside the BM differential count.ResultsThe frequencies of cells’ populations were correlated to the IG/N ratio, highlighting a mild correlation with MCs and erythroblasts (R=0.25 and R=0.38 respectively, with p-value=0.0006 and 0.0000052), whereas no significant correlation was found with B or T-cells. The mild correlation between IG/N, erythroblasts and MCs supported the combined use of these parameters to evaluate BM hemodilution, hence the optimization of the ALLgorithMM. Once validated, the ALLgorithMM was employed to evaluate the dilution status of BM samples in the context of MRD assessment. Overall, we found that 32% of FC and 52% of Next Generation Sequencing (NGS) analyses were MRD negative in samples resulted hemodiluted (HD) or at least mildly hemodiluted (mHD).ConclusionsThe high frequency of MRD-negative results in both HD and mHD samples implies the presence of possible false negative MRD measurements, impairing the correct assessment of patients’ response to therapy and highlighs the importance to evaluate BM hemodilution.

Revisiting the most often used item in the haematological tool box—The extent of haemodilution in bone marrow aspirates

“…Peter Hokland relevant when a minimal residual disease detection is sought for. 5,10 To what extent these extremely well-controlled Japanese findings can be transferred to your own setting is dependent upon how much your routines resemble those described. However, there is no doubt whatsoever that we can all learn from the errors delineated, which are cogently summarized by the authors.…”

“…Not only that, but they highlight the equal importance of acquiring suitable aspirates in follow‐ups. This is especially relevant when a minimal residual disease detection is sought for 5,10 …”

Role of flow cytometric measurable residual disease assessment in multiple myeloma

“…due to treatment. Therefore, it is necessary to develop a method with greater specificity to define hemodilution in BM, and the indications for repeated BM aspiration have not yet been clearly defined [39,40].…”