МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ

Recently, the identification of minimal residual disease (MRD), also known as measurable residual disease, has seen significant advances driven by the evolving technological landscape in this field. Initially based on raw morphology, the field has since evolved to incorporate karyotyping, cytogeneti...

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Бібліографічні деталі
Опубліковано в:Експериментальна онкологія
Дата:2026
Том:48
Випуск:2
Сторінки:98-107
ISSN:2312-8852
Автори та афіліації:
  • Sara Addakiri — Hassan II University of Medicine and Pharmacy, Casablanca, Morocco — ORCID: 0009-0008-5751-9846
  • Hanaa Bencharef — Hassan II University of Medicine and Pharmacy, Casablanca, Morocco — ORCID: 0000-0002-0086-0815
  • Asmaa Harrach — Hassan II University of Medicine and Pharmacy, Casablanca, Morocco — ORCID: 0000-0002-7524-0688
  • Samiha Jaddaoui — Hassan II University of Medicine and Pharmacy, Casablanca, Morocco
  • Khadija Ait-Ichou — IBN ROCHD Hospital Centre, Casablanca, Morocco
  • Bouchra Oukkache — Hassan II University of Medicine and Pharmacy, Casablanca, Morocco — ORCID: 0000-0003-2022-1938
Автори: Addakiri, Sara, Bencharef, Hanaa, Harrach, Asmaa, Jaddaoui, Samiha, Ait-Ichou, Khadija, Oukkache, Bouchra
Формат: Стаття
Мова:Англійська
Опубліковано: PH Akademperiodyka 2026
Онлайн доступ:https://exp-oncology.com.ua/index.php/Exp/article/view/640
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Назва журналу:Experimental Oncology
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Experimental Oncology
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author Addakiri, Sara
Bencharef, Hanaa
Harrach, Asmaa
Jaddaoui, Samiha
Ait-Ichou, Khadija
Oukkache, Bouchra
author_facet Addakiri, Sara
Bencharef, Hanaa
Harrach, Asmaa
Jaddaoui, Samiha
Ait-Ichou, Khadija
Oukkache, Bouchra
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description Recently, the identification of minimal residual disease (MRD), also known as measurable residual disease, has seen significant advances driven by the evolving technological landscape in this field. Initially based on raw morphology, the field has since evolved to incorporate karyotyping, cytogenetics, flow cytometry, and other sensitive methods. This updated review discusses key technical considerations for successful MRD detection. We explore the correlation between the results obtained by flow cytometry and molecular genetic techniques.
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fulltext 98 ISSN 1812-9269. Experimental Oncology 48 (2). 2026 ■ C i t a t i o n: Addakiri S, Bencharef H, Harrach A, Jaddaoui S, Ait-Ichou K, Oukkache B. Minimal residual disease assess- ment in acute lymphoblastic leukemia: Methods for detection and quantification. Exp Oncol. 2026; 48(2): 98-107. https:// doi.org/10.15407/exp-oncology.2026.02.098 © PH “Akademperiodyka” of the NAS of Ukraine, 2026. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Acute lymphoblastic leukemia (ALL) is a clonal di sease of hematopoietic stem cells of either B- or T-cell lineage. It manifests as lymphoblastoid cells with blocked differentiation. Despite being rare, ALL is the most common type of leukemia in children, affecting 4—5 children per 100,000 annually [1]. Precursor B‑cell ALL accounting for about 85% to 90% of ALL cases in children is more common than T-cell precur- sor ALL. T‑cell precursor leukemia accounts for 10%—15% of cases in children and 25% in adults, with T-lymphoblastic lymphoma (T-LBL) more prev- alent than B-LBL [1, 2]. The therapeutic strategy in- volves three stages, including induction, consolida- tion, and maintenance [3]. In children with B-ALL, the five-year disease-free survival rate exceeds 85%, with a cure rate of 90% [4, 5]. Similarly, in children with T‑ALL, the ffive-year event-free survival (EFS) rate has increased from 75% to > 90% [6]. However, a proportion of patients exhibit more risk factors, higher relapse probabilities, and, consequently, an unfavorable overall condition. In 1993, the National Cancer Center identified risk factors for childhood B-ALL for prognostic purposes. These factors in- clude age, white blood cell count, central nervous sys- tem involvement, cytogenetic alterations, aneuploidy, and early response to therapy. These factors reliably predict patient outcomes, and risk stratification was developed based on EFS. In contrast, risk factors for REVIEW https://doi.org/10.15407/exp-oncology.2026.02.098 Sara Addakiri 1, 2, *, Hanaa Bencharef 1, 2, Asmaa Harrach 1, 2, Samiha Jaddaoui 1, 2, Khadija Ait-Ichou 2, Bouchra Oukkache 1, 2 1 Hassan II University of Medicine and Pharmacy, Casablanca, Morocco 2 IBN ROCHD Hospital Centre, Casablanca, Morocco * Correspondence: E-mail: saraaddakiri1995@gmail.com MINIMAL RESIDUAL DISEASE ASSESSMENT IN ACUTE LYMPHOBLASTIC LEUKEMIA: METHODS FOR DETECTION AND QUANTIFICATION Recently, the identification of minimal residual disease (MRD), also known as measurable residual disease, has seen significant advances driven by the evolving technological landscape in this field. Initially based on raw morphology, the field has since evolved to incorporate karyotyping, cytogenetics, flow cytometry, and other sensitive methods. This up- dated review discusses key technical considerations for successful MRD detection. We explore the correlation between the results obtained by flow cytometry and molecular genetic techniques. Keywords: MRD, flow cytometry, molecular technique. https://doi.org/10.15407/exp-oncology.2026.02.098 https://doi.org/10.15407/exp-oncology.2026.02.098 https://creativecommons.org/licenses/by-nc-nd/4.0/ https://doi.org/10.15407/exp-oncology.2026.02.098 mailto:saraaddakiri1995@gmail.com ISSN 1812-9269. Experimental Oncology 48 (2). 2026 99 Minimal Residual Disease Assessment in Acute Lymphoblastic Leukemia: Methods for Detection and Quantification T-ALL are less well-defined [7]. Previous research by the Pediatric Oncology Group (POG) indicates that, unlike in B-ALL, advanced age and a high white blood cell count are not reliable indicators in T-ALL [8]. However, POG has observed a correlation bet ween T-cell maturation and patient outcomes. This discovery has been the focus of multiple studies, in- cluding the ALL 2000 study at St. Jude Children’s Re- search Hospital, which provided deeper insights into this association [9]. A pivotal question in the man- agement of ALL in children is identifying those who require more intensive therapy to mitigate the risk of relapse. Clinical and biological factors, such as white blood cell count, age, immunophenotype, ploidy, structural chromosomal abnormalities, and genetic rearrangements, can be used to stratify treatment, al- though these factors are not ideal. While some pa- tients with promising indicators experience recur- rence, others at a higher risk of relapse receive more intensive treatment than necessary. Several studies focused on minimal residual di sease (MRD) to obtain more reliable estimates of lymphoblast counts during the clinical remission phase. MRD serves as an indicator of treatment sen- sitivity and intensity, enabling the adoption of tai- lored treatment protocols. The reliable detection of MRD aims to identify children at high risk of relapse as early as possible. Additionally, it is used to assess bone marrow and peripheral blood for the suitability of autologous hematopoietic stem cell transplanta- tion. Moreover, MRD plays a crucial role in evalua ting the clearance process [10]. Finally, MRD allows for comparing the effectiveness of different chemo- therapy regimens. This paper aims to provide a com- prehensive overview of MRD identification tech- niques. Indeed, one of the major challenges in child- hood ALL is identifying those who require more intensive treatment to prevent the risk of relapse. During the clinical remission phase, MRD assess- ment contributes significantly to improving the quantification of the total burden of leukemia cells. This is crucial as it indicates disease aggressiveness and treatment sensitivity, thus facilitating the selec- tion of the most appropriate therapeutic strategy. MRD detection and quantification methods An effective platform for identifying MRD must possess three key advantages encompassing opti- mal sensitivity, specificity, and reproducibility [11]. Despite advances in immunohistochemistry testing methods, morphological assessment remains insuf- ficient in terms of sensitivity and specificity. Simi- larly, traditional methods such as karyotyping and fluorescence in situ hybridization lack the required sensitivity to detect submicroscopic leukemia cells, often achieving detection rates as low as 1%—5% [12]. The primary techniques used to assess MRD include flow cytometry, which relies on identifying cells with abnormal immunophenotypes, and mo- lecular genetic methods such as polymerase chain reaction (PCR) for identifying tumor-specific anti- gen receptor sequences. Today, next-generation se- quencing (NGS) has emerged as another valuable tool for molecularly identifying these genetic ab- normalities [13]. The accuracy and scope of MRD tests are undergoing significant changes, driven by the development of improved antibodies, upgrades to flow cytometers, and advancements in comput- ing [14]. Flow cytometry has revealed significant correlations between MRD findings, treatment ef- ficacy, and clinical features, thereby enhancing the credibility of this approach [15—18]. Flow cytom- etry, with its accessibility and straightforward con- cept, stands out as the most readily available tech- nique for identifying MRD [19]. It directly mea- sures MRD, simplifying quantification and enabling more precise measurements [20]. More- over, flow cytometry can also detect dying cells and cellular fragments. This is particularly useful for analyzing fresh samples (e.g., those collected with- in several hours) because it allows researchers to identify cell death caused by a lack of survival fac- tors before spontaneous cell death occurs. Never- theless, the application of flow cytometry may have several limitations. To identify a single leukemia cell among 105 or more normal cells is challenging with flow cytometry but achievable with PCR. This level of sensitivity is particularly valuable in MRD studies involving patients with irregular disease distribution, as well as in the context of cell collec- tion for autograft procedures. It is also important to note that the immunophenotype of leukemia cells evolves as the disease progresses. However, if these changes affect the markers used for MRD surveillance, there is a risk of obtaining false-neg- ative results [14, 21—23]. This risk is inversely pro- portional to the number of marker combinations applicable to each patient. In other words, if cells 100 ISSN 1812-9269. Experimental Oncology 48 (2). 2026 S. Addakiri, H. Bencharef, A. Harrach, S. Jaddaoui, K. Ait-Ichou, B. Oukkache exhibit multiple suitable phenotypes, the loss of one phenotypic pattern can be compensated by the per- sistence of other abnormal patterns. Another limita- tion of flow cytometry techniques is that their results rely on the analysis of immunophenotypic charac- teristics of leukemia, while immunophenotype may change substantially between diagnosis and relapse. These frequent changes complicate the use of the original diagnostic markers for targeted MRD detec- tion by flow cytometry [23]. Immature T cells are homologs of normal T-cell lineage ALL cells. Unlike leukemic T-cell lympho- blasts, which circulate freely throughout the body, these cells are limited to the thymus. To detect MRD in patients with T-cell lineage ALL, the focus is on identifying cells with the immature T-cell phenotype in bone marrow or peripheral blood. Ef- fective immunophenotypes for this purpose in- volve the simultaneous expression of T-cell mar kers such as CD3, CD5, and either TdT or CD34 [24]. Some studies also suggest that certain combi- nations of antibodies, such as CD7 and CD3 with CD2 or CD5, may exhibit abnormal expression in a subset of T-ALL patients [25, 26]. B cell progeni- tors, which are the normal counterparts of B-cell lineage ALL cells, are primarily found in the bone marrow and in smaller quantities in peripheral blood [25]. Therefore, MRD studies in the B-cell ALL lineage require distinguishing between leuke- mia cells and their normal counterparts, which can be achieved by examining abnormal levels of ex- pression of various molecules in leukemia cells [25—27]. T-ALL MRD backbone panels are set up to evaluate both the aberrant expression of mature T/NK-cell antigens (i.e., surface/cytoplasmic CD3, CD5, CD7, CD2, CD4, CD8, CD45, CD16, and CD56) and immature markers (CD34, CD1a, TdT, and CD99) These immature markers are frequent- ly absent or very dim, and CD45 is commonly quite bright in the residual leukemic cells after treatment. It is hard to say whether the immature nature of residual T-ALL and the “different-from-normal” strategies are available to identify a T-cell popula- tion different from normal T cells [28]. In most cases, the second strategy includes looking for ab- normal CD4/8 double-negative (DN), CD4/8 dou- ble-positive (DP), and/or sCD3–cCD3+ cells. In the context of B-ALL, markers such as CD13, CD15, CD33, and CD65 myeloid markers, along with the CD21 marker, associated with mature B cells, have the potential to be expressed by CD19+CD34+ cells. Conversely, normal CD19+CD34+ B cell progenitors do not express these markers or express them only weakly [25]. When comparing B-ALL to their nor- mal counterparts, the expression levels of CD19, CD10, TdT, and CD34 vary considerably, either be- ing higher or lower [29]. Leukemia cells often ex- hibit underexpression of CD38 and CD45. The EuroFlow consortium is currently developing ad- vanced protocols for flow cytometry, known as Next Generation Flow [30]. These protocols aim to establish standards for MRD detection [31]. The first step involves a mass lysis procedure to remove erythrocytes and concentrate leukocytes, thereby increasing the number of cells available for label- ing. While traditional four-color flow cytometry has a sensitivity of 0.01%, this new technique achieves a sensitivity of 0.001% due to its ability to label more than 4 × 106 cells [32]. The Children’s Oncology Group (COG) has a standardized 3-tube 6-color panel for B-ALL MRD detection, which is used for patients in COG studies. This panel in- cludes CD34, CD19, CD10, CD20, CD38, CD45, CD9, CD58, CD13/33, CD71, CD3, and Syto16. Although it has limitations such as not being able to detect CD19-negative MRD due to its gating strategy and consuming more samples, it is highly standardized with a good sensitivity (10–4) in most cases. A highly sensitive standardized multipara meter flow cytometry (MFC) B‑ALL MRD assay has also been designed by the EuroFlow group, and it demonstrates the application of a fully standardized bulk lysis protocol and two stepwise- designed 8-color tubes (including the backbone panel plus CD81 and either CD66c/CD123 or CD73/CD304) [33]. The inclusion of B‑cell mark- ers other than CD19 has been emphasized in recent years due to the increasing clinical use of immu- notherapies targeting CD19 (i.e., blinatumomab and CAR-T19). CD22 and CD24 are expressed in B lymphoblasts and can be essential for tracking B-ALL leukemic cells with downregulation of CD19 as well as for identification of CD22+ cases eligible for inotuzumab ozogamicin therapy [34]. In summary, flow cytometry is used in more than 95% of patients and provides valuable information on the immunophenotypic heterogeneity of leuke- mia and the cellular state of the bone marrow micro- environment — aspects that are insufficiently con- sidered by other MRD techniques [32]. While flow ISSN 1812-9269. Experimental Oncology 48 (2). 2026 101 Minimal Residual Disease Assessment in Acute Lymphoblastic Leukemia: Methods for Detection and Quantification cytometry has lower costs and faster turnaround time (1 day) compared to the alternative approaches mentioned below (4 days to weeks), it involves rapid manipulation due to its execution on living cells. Ad- ditionally, achieving sensitivity levels above 10–5 re- quires a significant quantity of cells [30, 35]. Real-time quantitative PCR (RQ-PCR) The use of RQ-PCR is an accurate method to iden- tify MRD, with sensitivity potentially reaching le vels as low as 10–6. When using PCR to identify MRD, the genetic marker typically employed to dif- ferentiate ALL from healthy cells is the rearranged sequence of the Ig/TCR gene or fusion gene. Rearrangements of immunoglobulin and T cell receptor genes can be used to identify a small num- ber of ALL cells among a large population of normal lymphocytes expressing different gene rearrange- ments. In B-cell precursor ALL, incomplete and complete IGH, IGK, and IGL rearrangements are more commonly detected and used as MRD targets. However, sometimes leukemia cells of the B- and T-lineage display lineage rearrangements, identifi- able by multipoint PCR and usable for the determi- nation of MRD [36, 37]. Sequencing of PCR prod- ucts is performed to determine junctional regions and acquire allele-specific primers, with successful cloning confirmation through homo-heteroduplex analysis [38, 39]. This qPCR technique, using fluo- rescent marker-labelled probes, is extremely accu- rate, capable of identifying one leukemia cell among 100,000 healthy lymphoid cells under ideal circum- stances [40]. The EuroMRD consortium, a dedicat- ed group of expert laboratories, has played an im- portant role in establishing the most widely accept- ed MRD approach. This consortium offers training, standardization, quality control, and guidelines for the interpretation of RQ-PCR data [41]. MRD ex- periments conducted in EuroMRD laboratories can be reliably replicated, allowing for the comparison of MRD datasets from different clinical protocols. However, due to its complexity, the identification of a small leukemia population using this MRD ap- proach requires specialized knowledge and exper- tise [42]. Additionally, technical issues hinder the identification of MRD targets in 5%–10% of cases using RQ-PCR-based MRD. This method has a lim- itation related to the possibility of false-negative MRD results due to clonal evolution of Ig/TCR re- arrangements during the disease and relapse. The study by Szczpansky et al. [43] demonstrated that 22% of leukemia patients lost most or all their Ig/ TCR targets assessed at diagnosis after the onset of hematological relapse. The amount of diagnostic DNA available for analysis is another limitation for this type of MRD assessment. Since it quantifies tu- mor burden at diagnosis, the initial DNA sample obtained at the first diagnosis is required for each MRD experiment and the identification of Ig/TCR clonal rearrangements [44]. Identification of the fusion gene. Precise identifi- cation of leukemia subtypes containing fusion genes is achieved using RQ-PCR. However, this method is reliable for only 40% of patients with ALL distinct characteristics and molecular abnormalities. Among pediatric cases of ALL, four prevalent types of fusion genes should be distinguished: • The TEL/AML1 fusion gene (also known as ETV6-RUNX1) from the t(12;21)(p13;q22) trans- location. It occurs in 22% of children and 2% of adults with ALL [45]. This translocation is the most common in childhood B-ALL. Moreover, it is as- sociated with an excellent prognosis with intensive chemotherapy, including asparaginase therapy. • The TCF3/PBX1 fusion gene from the t(1;19) (q23;p13) translocation represents 5% of childhood ALL and 3% of adult ALL and is frequently associ- ated with the pre-B immunophenotype, in about 25% of cases [45, 46]. • BCR/ABL from the t(9;22)(q34;q11) transloca- tion is found in approximately 3% of children and 30% of adults, and is associated with an unfavor- able prognosis [46]. • AF4/MLL is derived from the t(4;11)(q21;q23) translocation [45,46]. Chromosomal rearrange- ments of the human MLL gene are the most com- mon genetic abnormality in the first year of life, but it occurs in only 8% of children and 10% of adults with ALL [46]. The first two fusion genes have higher incidence rates in children with B-ALL. In contrast, the BCR/ ABL fusion gene is more frequently found in chronic myeloid leukemia and remains rare in pe- diatric ALL. In more than 2/3 of childhood leuke- mia cases, the AF4/MLL fusion gene is present. Ac- cording to Ajuba et al. [47], this fusion gene is as- sociated with poor prognosis and is predominant in B-ALL of infants. 102 ISSN 1812-9269. Experimental Oncology 48 (2). 2026 S. Addakiri, H. Bencharef, A. Harrach, S. Jaddaoui, K. Ait-Ichou, B. Oukkache discovered identifiable clonal rearrangements in 93% of patients in the pretreatment sample [49, 50]. Among MRD-positive cases, the clone most frequently identified in the pretreatment sample corresponds to the equally dominant clone on day 29. Like in T-ALL, a subset of MRD patients was identifiable by NGS but not by flow cytometry. Patients without clonal rearrangements of the Im- munoglobulin Superfamily had poorer outcomes than patients with clonal IGH. Maybe these cases represent more primitive clones [51]. NGS offers several advantages over flow cytometry and con- ventional PCR when examining MRD. It involves less subjectivity in interpretation compared to flow cytometry. Once the protocol is established, the technical requirements are easier than those of other molecular genetic methods. By using primers to simultaneously amplify any possible combination of rearranged IGH or TCR loci, NGS bypasses the need for patient-specific primers. This explains the use of HTS because of its speed in real-time therapeutic decision-making, al- though it is slower than flow cytometry in practi- cal applications. However, NGS can only identify cases with complete rearrangements, leaving be- hind a limited number of cases without rearrange- ments or with incomplete rearrangements. In ad- dition, this method involves matching pre- and post-processing samples. Several studies demon- strated that NGS can accurately predict the rate of recurrence and survival by detecting MRD as compared to flow cytometry and conventional PCR [50] and can potentially replace these me thods in the future [52, 53]. New technologies Despite significant progress in standardizing RQ- PCR for MRD detection and ensuring reproduc- ibility within and between laboratories, there are still two main concerns that need to be addressed. One is related to the significant amount of DNA required for accurate diagnosis. The other pertains to the risk of non-specific amplification in RQ-PCR technology, especially in the presence of low levels of MRD. Indeed, a substantial amount of diagnostic DNA is essential for the detection of clonal rear- rangements in MRD genes by IG/TR. This is be- cause, in addition to early detection of clonal rear- rangements, a standard dilution curve must be con- Variations in the detection rates of different fu- sion genes in different regions are observed. This is probably a result of genetic diversity among breeds. Although RQ-PCR has some advantages, such as simple and fast operation, high specificity, and sen- sitivity in the detection of fusion genes, it is limited to specific subtypes of leukemia. The variations in the expression of fusion genes between individuals and the potential for false-positive results due to PCR contamination are additional challenges. Fur- thermore, RQ-PCR faces difficulties in achieving accurate ratios between the number of leukemia cells and PCR products, making it inadequate for precise cellular-level MRD assessment. Next Generation Sequencing (NGS) In the late 1990s, new DNA sequencing tech- niques emerged. These methods were further de- veloped into high-throughput sequencing (HTS), known as NGS, since 2000. This has rapidly gained adoption by researchers in various fields. The advantages of NGS are twofold: it can se- quence large amounts of DNA quickly and has a sensitivity to detect and quantify very small clones, such as one cell in a population of 10-6 cells, as well as very low-frequency cells. Re- searchers have been particularly interested in ex- ploring the use of NGS for MRD detection. Ini- tially, they used this method to detect MRD in T-ALL and then in B-ALL [48, 49]. NGS in the context of T-ALL. Wu et al. [48] used HTS to study MRD in patients diagnosed with T‑ALL and compared these results with those ob- tained by flow cytometry. HTS showed better sen- sitivity in detecting MRD. Interestingly, among cas- es without TCR clonal beta rearrangements at di- agnosis, some had substantial clones identifiable by flow cytometry on day 29. Almost half of these cas- es had an immunophenotype of early T-cell precur- sors (ETP), while the other half had a similar phe- notype, except for the presence of CD5, which is referred to as ‘quasi-ETP’. Conversely, none of the cases with detectable TCR clonal beta rearrange- ments had an ETP phenotype. NGS in the context of B-ALL. In line with pre- vious research on T-ALL, NGS was used for MRD detection in patients with B-ALL [49]. NGS was extended to all B-ALL patients, regardless of their known IGH rearrangements [50]. The authors ISSN 1812-9269. Experimental Oncology 48 (2). 2026 103 Minimal Residual Disease Assessment in Acute Lymphoblastic Leukemia: Methods for Detection and Quantification Detection methods used to monitor MRD in ALL Method Advantages Disadvantages FCM (Flow cytometry) Fast Sensitivity 10–4 Relatively inexpensive Ability to quantify Aberrant antigen expression Variable sensitivity due to similarities between normal (regenerating) cells and malignant cells Limited standardization, no QA (quantification) results FCM-DfN (Flow cytometry different from normal) Sensitivity 10–3 to 10–5 No diagnostic sample required Phenotypic shifts will not interfere with results Applicable to > 90% of patients Rapid turnaround time Significant operator experience required Limited standardization RT-PCR of fusion genes Sensitivity 10–4 to 10–5 Simple (uses some primers as used for diagnosis) Limited QA rounds Limited applicability in ALL (absence of targets in 50% of cases) Risk of contamination PCR of Ig/TCR genes Sensitivity 10–4 to 10–5 Applicable to most patients Standardized guidelines in Europe Time-consuming Expensive Relies on pre-treatment sample Requires extensive experience and labor Digital PCR Highly sensitive (10–4 to 10–5) Rapid and widely applicable Limited standardization, available only in a few labs, no approved guidelines for data analysis, relatively expensive Next Generation Sequencing Very sensitive (10–6) Applicable to almost all patients Clone–unbiased (can track multiple clones and evolution) Only US FDA-approved assay (ClonoSEQ) Data for MRD use in peripheral blood Expensive Longer turnaround time than FCM Requires diagnostic pre-treatment sample structed for each qPCR MRD experiment, posing limitations in monitoring patients, especially when assessing multiple time points. Third-generation PCR, known as droplet digital PCR (ddPCR), makes it possible to overcome these limitations of conventional RQ-PCR. ddPCR technology com- partmentalizes the sample into thousands of indi- vidual droplets, each representing an independent PCR reaction. This allows for endpoint amplifica- tion and utilizes Poisson statistics [54, 55]. Several studies on medical diagnosis focused on the use of ddPCR techniques in oncology, including hemato- logical malignancies [56, 57]. The recent studies compared ddPCR and qPCR in adult patients with mature lymphoid malignancies and adolescent and young adult patients with ALL, respectively [58], and reported that ddPCR exhibits sensitivity, ac- curacy, and reproducibility comparable to qPCR. Moreover, ddPCR technology made it possible to determine the absolute amount of specific DNA molecules in a given sample without the need to compare to a standard curve. While the final clini- cal validations of ddPCR are still pending, the first guidelines for interpreting ddPCR data in a clinical setting have been published [59]. ddPCR can certainly serve as a viable alternative to qPCR and as an instrument to preserve DNA samples. Owing to the extensive partitioning of the reaction mixture into a large number of individual compartments, ddPCR can achieve a very high le vel of analytical precision. Furthermore, ddPCR is particularly well suited for the detection of low- abundance targets in the presence of a high back- ground of non-target DNA. Within partitions that contain the target molecule, the relative proportion of target to non-target DNA becomes significantly higher than in the original sample, thereby facilita ting detection. 104 ISSN 1812-9269. Experimental Oncology 48 (2). 2026 S. Addakiri, H. Bencharef, A. Harrach, S. Jaddaoui, K. Ait-Ichou, B. Oukkache REFERENCES 1. Swerdlow SH, Campo E, Pileri SA, et al. 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Blood. 2014;124(21):1. https://doi.org/10.1182/blood.V124.21.1.1 Finally, dPCR amplification — and consequent- ly, the resulting quantification — is generally less affected by partial PCR inhibition compared to conventional PCR. Several digital PCR (dPCR) platforms are currently available on the market, reflecting the growing importance of this relatively recent technology in quantitative molecular biol- ogy applications. Existing dPCR instruments can be broadly categorized according to their partitio ning formats. Amplification of non-specific, false Ig/TCR rear- rangements cannot be distinguished from cases of very low-level positive results that cannot be quan- tified. These non-quantifiable positive cases present a risk of detecting false positives or false negatives in the analysis of MRD, creating an additional chal- lenge. In this context, the EuroMRD recommenda- tions are aimed at the management of non-specific amplification, considering different clinical objec- tives. These guidelines focus on the prevention of false negatives or false positives [60]. In any case, it is important to evaluate the results carefully, espe- cially for samples collected after treatment has been completed or after HSCT. Indeed, the identification of MRD in these situations can be complicated by the reconstitution of B cells. In such circumstances, a specific study of the size or profile of the RQ-PCR is necessary before making a medical decision [61]. HTS based on PCR of Ig/TCR gene rearrangements represents an interesting advance in this context. HTS identifies clone-specific IG/TR indexing se- quences. The same procedure is used for each fol- low-up copy, allowing the determination and quan- tification of clones detected during diagnosis [62]. Several recent studies highlighted the greater spe cificity of HTS in identifying recurrence in ALL pa- tients following HSCT [63] or induction [64] com- pared to RQ-PCR. HTS for MRD detection also has the advantage of allowing early identification of clonal evolution, which is a relatively common phe- nomenon in recurrent ALL [65]. With the use of universal primers, this technique allows simultane- ous monitoring of all Ig/TCR gene rearrangements, providing a global view of MRD as well as the nor- mal immune repertoire. However, to date, stan- dardization of HTS MRD is very limited, and guidelines for interpreting the information are not yet available. The working group of the Euroclona lity-NGS consortium is working to fill this gap. At the same time, the practicability of HTS MRD is dependent on cost and complexity, although this tends to diminish [66]. The methods in current use for monitoring MRD in ALL are summarized in the Table. To sum up, in clinical practice, incorporating MRD follow-up as a component of the initial treatment regimen is routine for nearly all cases of ALL in children and a substantial portion of adult cases as well. 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Leukemia. 2014;28(6):1299-1307. https://doi.org/10.1038/ leu.2013.375 Submitted: September 10, 2025 Сара Аддакірі 1, 2, Ханаа Бенчареф 1, 2, Асмаа Харрах 1, 2, Саміха Джаддауї 1, 2, Хадіжа Айт-Ічу 2, Бушра Уккаче 1, 2 1 Медико-фармацевтичний факультет университету Хасана ІІ, Касабланка, Марокко 2 Університетський медичний центр Ібн Рошд, Касабланка, Марокко МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ Ідентифікація мінімальної залишкової хвороби (МЗХ) зазнала значного прогресу завдяки розвитку технологій, застосованих у цій галузі. Якщо спочатку вона базувалася виключно на морфології, згодом методологія визна- чення МЗХ зазнала докорінних змін та включила каріотипування, цитогенетику, проточну цитометрію та інші чутливі методи. В огляді обговорено ключові технічні аспекти успішного виявлення МЗХ i проаналізовано коре- ляцію між результатами, отриманими за допомогою проточної цитометрії та молекулярно-генетичних методів. 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spelling oai:ojs2.ex.aqua-time.com.ua:article-6402026-08-21T12:36:20Z MINIMAL RESIDUAL DISEASE ASSESSMENT IN ACUTE LYMPHOBLASTIC LEUKEMIA: METHODS FOR DETECTION AND QUANTIFICATION МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ Addakiri, Sara Bencharef, Hanaa Harrach, Asmaa Jaddaoui, Samiha Ait-Ichou, Khadija Oukkache, Bouchra MRD, flow cytometry, molecular technique Recently, the identification of minimal residual disease (MRD), also known as measurable residual disease, has seen significant advances driven by the evolving technological landscape in this field. Initially based on raw morphology, the field has since evolved to incorporate karyotyping, cytogenetics, flow cytometry, and other sensitive methods. This updated review discusses key technical considerations for successful MRD detection. We explore the correlation between the results obtained by flow cytometry and molecular genetic techniques. дентифікація мінімальної залишкової хвороби (МЗХ) зазнала значного прогресу завдяки розвитку технологій, застосованих у цій галузі. Якщо спочатку вона базувалася виключно на морфології, згодом методологія визначення МЗХ зазнала докорінних змін та включила каріотипування, цитогенетику, проточну цитометрію та інші чутливі методи. В огляді обговорено ключові технічні аспекти успішного виявлення МЗХ i проаналізовано кореляцію між результатами, отриманими за допомогою проточної цитометрії та молекулярно-генетичних методів. PH Akademperiodyka 2026-08-21 Article Article application/pdf https://exp-oncology.com.ua/index.php/Exp/article/view/640 10.15407/exp-oncology.2026.02.098 Experimental Oncology; Vol. 48 No. 2 (2026): Experimental Oncology; 98-107 Експериментальна онкологія; Том 48 № 2 (2026): Експериментальна онкологія; 98-107 2312-8852 1812-9269 10.15407/exp-oncology.2026.02 en https://exp-oncology.com.ua/index.php/Exp/article/view/640/470 Copyright (c) 2026 Experimental Oncology https://creativecommons.org/licenses/by-nc-nd/4.0/
spellingShingle Addakiri, Sara
Bencharef, Hanaa
Harrach, Asmaa
Jaddaoui, Samiha
Ait-Ichou, Khadija
Oukkache, Bouchra
МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title_alt MINIMAL RESIDUAL DISEASE ASSESSMENT IN ACUTE LYMPHOBLASTIC LEUKEMIA: METHODS FOR DETECTION AND QUANTIFICATION
title_full МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title_fullStr МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title_full_unstemmed МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title_short МІНІМАЛЬНА ЗАЛИШКОВА ХВОРОБА ПРИ ГОСТРІЙ ЛІМФОБЛАСТНІЙ ЛЕЙКЕМІЇ: МЕТОДИ ВИЯВЛЕННЯ ТА КІЛЬКІСНОГО ВИЗНАЧЕННЯ
title_sort мінімальна залишкова хвороба при гострій лімфобластній лейкемії: методи виявлення та кількісного визначення
topic_facet MRD
flow cytometry
molecular technique
url https://exp-oncology.com.ua/index.php/Exp/article/view/640
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