The monocyte subset partitioning by flow cytometry, known as “monocyte assay,” is now integrated into the new classifications as a supporting criterion for CMML diagnosis, if a relative accumulation ...of classical monocytes above 94% of total circulating monocytes is observed. Here we provide clinical flow cytometry laboratories with technical support adapted for the most commonly used cytometers. Step‐by‐step explanations of the gating strategy developed on whole peripheral blood are presented while underlining the most common difficulties. In a second part, interpretation recommendations of circulating monocyte partitioning from the dedicated French working group “CytHem‐LMMC” are shared as well as the main pitfalls, including false positive and false negative cases. The particular flow‐defined inflammatory profile is described and the usefulness of the nonclassical monocyte specific marker, namely slan, highlighted. Examples of reporting to the physician with frequent situations encountered when using the monocyte assay are also presented.
Background: It was proposed that peripheral blood (PB) monocyte profiles evaluated by flow cytometry, called “monocyte assay,” could rapidly and efficiently distinguish chronic myelomonocytic ...leukemia (CMML) from other causes of monocytosis by highlighting an increase in the classical monocyte (cMo) fraction above 94%. However, the robustness of this assay requires a large multicenter validation and the assessment of its feasibility on bone marrow (BM) samples, as some centers may not have access to PB.
Methods: PB and/or BM samples from patients displaying monocytosis were assessed with the “monocyte assay” by 10 ELN iMDS Flow working group centers with harmonized protocols. The corresponding files were reanalyzed in a blind fashion and the cMo percentages obtained by both analyses were compared. Confirmed diagnoses were collected when available.
Results: The comparison between cMo percentages from 267 PB files showed a good global significant correlation (r = 0.88) with no bias. Confirmed diagnoses, available for 212 patients, achieved a 94% sensitivity and an 84% specificity. Hence, 95/101 CMML patients displayed cMo ≥94% while cMo <94% was observed in 83/99 patients with reactive monocytosis and in 10/12 patients with myeloproliferative neoplasms (MPN) with monocytosis. The established Receiver Operator Curve again provided a 94% cut‐off value of cMo. The 117 BM files reanalysis led to an 87% sensitivity and an 80% specificity, with excellent correlation between the 43 paired samples to PB.
Conclusions: This ELN multicenter study demonstrates the robustness of the monocyte assay with only limited variability of cMo percentages, validates the 94% cutoff value, confirms its high sensitivity and specificity in PB and finally, also confirms the possibility of its use in BM samples.
Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/ myeloproliferative neoplasm whose diagnosis is currently based on the elevation of peripheral blood monocytes to >1 × 109/L, ...measured for ≥3 months. Diagnosis can be ambiguous; for example, with prefibrotic myelofibrosis or reactive monocytosis. We set up a multiparameter flow cytometry assay to distinguish CD14+/CD16− classical from CD14+/CD16+ intermediate and CD14low/CD16+ nonclassical monocyte subsets in peripheral blood mononucleated cells and in total blood samples. Compared with healthy donors and patients with reactive monocytosis or another hematologic malignancy, CMML patients demonstrate a characteristic increase in the fraction of CD14+/CD16− cells (cutoff value, 94.0%). The associated specificity and sensitivity values were 95.1% and 90.6% in the learning cohort (175 samples) and 94.1% and 91.9% in the validation cohort (307 samples), respectively. The accumulation of classical monocytes, which demonstrate a distinct gene expression pattern, is independent of the mutational background. Importantly, this increase disappears in patients who respond to hypomethylating agents. We conclude that an increase in the fraction of classical monocytes to >94.0% of total monocytes is a highly sensitive and specific diagnostic marker that rapidly and accurately distinguishes CMML from confounding diagnoses.
•An increase in the classical monocyte subset to >94% of total monocytes discriminates CMML from other monocytoses with high specificity.•This characteristic increase in classical monocytes disappears in CMML patients who respond to hypomethylating agents.
Loss-of-function mutations affecting one or both copies of the
Ten-Eleven-translocation (
TET)
2 gene have been described in various human myeloid malignancies. We report that inactivation of
Tet2 in ...mouse perturbs both early and late steps of hematopoiesis including myeloid and lymphoid differentiation in a cell-autonomous manner, endows the cells with competitive advantage, and eventually leads to the development of malignancies. We subsequently observed
TET2 mutations in human lymphoid disorders.
TET2 mutations could be detected in immature progenitors endowed with myeloid colony-forming potential. Our results show that the mutations present in lymphoid tumor cells may occur at both early and later steps of lymphoid development and indicate that impairment of TET2 function or/and expression predisposes to the development of hematological malignancies.
►
TET2 inactivation in mice affects HSC homeostasis and differentiation ►
TET2 inactivation in mice leads to a CMML-like disease ►
TET2 is mutated in human B and T cell lymphomas
IDH1 and IDH2 somatic mutations have been identified in solid tumors and blood malignancies. The development of inhibitors of mutant IDH1 and IDH2 in the past few years has prompted the development ...of a fast and sensitive assay to detect IDH1R132, IDH2R140 and IDH2R172 mutations to identify patients eligible for these targeted therapies. This study aimed to compare two new multiplexed PCR assays – an automated quantitative PCR (qPCR) on the PGX platform and a droplet digital PCR (ddPCR) with next‐generation sequencing (NGS) for IDH1/2 mutation detection. These assays were evaluated on 102 DNA extracted from patient peripheral blood, bone marrow and formalin‐fixed paraffin‐embedded tissue samples with mutation allelic frequency ranging from 0.6% to 45.6%. The ddPCR assay had better analytical performances than the PGX assay with 100% specificity, 100% sensitivity and a detection limit down to 0.5% on IDH1R132, IDH2R140 and IDH2R172 codons, and a high correlation with NGS results. Therefore, the new highly multiplexed ddPCR is a fast and cost‐effective assay that meets most clinical needs to identify and follow cancer patients in the era of anti‐IDH1/2‐targeted therapies.
This study presents the first evaluation of two new highly multiplexed PCR assays as compared with next‐generation sequencing (NGS): an automated qPCR on the PGX platform and an allele‐specific droplet digital PCR (ddPCR) assay, both designed to detect most IDH1 and IDH2 hotspot mutations. The ddPCR assay was the best assay in terms of sensitivity, specificity, robustness, cost and timeliness, regardless of patient sample processing. It is, therefore, an appealing alternative to NGS to screen patients eligible for IDH1/2 targeted therapies.
Background
Flow cytometry (FCM) aids the diagnosis and prognostic stratification of patients with suspected or confirmed myelodysplastic syndrome (MDS). Over the past few years, significant progress ...has been made in the FCM field concerning technical issues (including software and hardware) and pre‐analytical procedures.
Methods
Recommendations are made based on the data and expert discussions generated from 13 yearly meetings of the European LeukemiaNet international MDS Flow working group.
Results
We report here on the experiences and recommendations concerning (1) the optimal methods of sample processing and handling, (2) antibody panels and fluorochromes, and (3) current hardware technologies.
Conclusions
These recommendations will support and facilitate the appropriate application of FCM assays in the diagnostic workup of MDS patients. Further standardization and harmonization will be required to integrate FCM in MDS diagnostic evaluations in daily practice.
This article discusses the rationale for inclusion of flow cytometry (FCM) in the diagnostic investigation and evaluation of cytopenias of uncertain origin and suspected myelodysplastic syndromes ...(MDS) by the European LeukemiaNet international MDS Flow Working Group (ELN iMDS Flow WG). The WHO 2016 classification recognizes that FCM contributes to the diagnosis of MDS and may be useful for prognostication, prediction, and evaluation of response to therapy and follow‐up of MDS patients.
Introduction: Since the publication of the International Guidelines (Borowitz, 2010; Illingworth, 2018), no study has assessed the long-term evolution of paroxysmal nocturnal hemoglobinuria (PNH) ...clones using high-resolution flow cytometry. The sole evaluation, performed by Sugimori et al, using a 2-color flow cytometry test, showed the disappearance of PNH clones in 24% of patients with bone marrow (BM) failure over 5 years (Sugimori, 2009). A diagnostic practice harmonization using high-resolution flow cytometry has spread in France since 2013 through an on-going inter-laboratory comparison program (Debliquis, 2015). Thus, our HPNAFC group has been able to initiate a French nation-wide multicenter prospective observational study.
Objective: We aimed to assess the evolution of PNH clones over a long term period using mostly high sensitivity test, which is required for minor clone assessment, with validated flow cytometry data.
Methods: All patients of any age with a PNH clone or GPI-deficient cells ≥0.01%, newly- or previously-diagnosed, detected in France from February 29th 2016, could be included in this Observatory, provided that the center had validated a PNH flow cytometry quality control. For each patient, the baseline assessment was always considered as the initial PNH clone detection, even if it occurred before the initiation of the Observatory. Thus, this strategy allowed the collection of cases with long-term follow-up. Referent cytometrist of each center included patients in the e-CRF available on the HPNAFC website providing clinical and biological information as well as flow cytometry raw data files. This study was approved by the national research ethics board.
Results: As of July 15th 2019, 48 participating flow cytometry laboratories across France have enrolled 356 patients with a PNH clone or GPI-deficient cells ≥ 0.01%. All cases have been carefully reviewed by the 2 principal investigators, who both thoroughly re-examined flow cytometry data and the e-CRF filling that led to the update of roughly one third of the submitted files. This enabled the validation of 200 patients at diagnosis, the remaining 156 being ongoing. One hundred and three of the 200 validated patients displayed at least one follow-up point (more than 3 months apart from the diagnosis) with a clone size determined at diagnosis (see flow chart figure 1A). For 8/103 patients, exchanges with centers are still ongoing. Thus, we were able to assess the evolution of PNH clones of 95 patients with 2 range: 1-8 follow-up points over a period of 4.1 0.3-14.2 years, corresponding to 200 validated follow-up points. The patient median age at diagnosis was 40 years old 10-85 with 3 pediatric cases (<18y) and a M/F sex ratio of 0.86. Diagnoses were made between 2003 and 2018 with clinical information available in 97% of cases: 19 patients (20%) had hemolytic anemia and most patients (n=73, 77%) displayed BM failure including aplastic anemia (n=62), myelodysplastic syndrome (n=7) and unexplained cytopenia(s) (n=4). No case of thrombosis was included. All patients with hemolytic anemia showed an increasing clone size over time including the two who were not treated with eculizumab (Figure 1B; median size at diagnosis on neutrophils: 81.3% vs median size over 5 years: 96.3%). The median clone size at diagnosis for patients with BM failure was 1.5% on neutrophils with a very wide range 0.01-97.87, almost half of them being less than 1%. When comparing the diagnosis point with the latest follow-up point, PNH clone size increased in 37 patients, decreased in 16 of them and remained stable in 20 cases (Figure 1C, D). Nine of the 37 patients reached a PNH clone size above 50% and 4 of them received a treatment by eculizumab in a median delay of 5 years 1.5-6.0. Interestingly, no patient showed spontaneous disappearance of PNH clones, pending the use of a high-resolution flow cytometry test. The only five patients with undetectable PNH clones (Figure 1D, red lines) were those who underwent BM transplantation.
Conclusion: This multicenter study based on robust flow cytometry analysis showed no disappearance of PNH clones, including minor ones, over a long period of time, regardless of the clinical manifestations, except for patients who underwent BM transplantation. Moreover, PNH clone size increased in half of patients with BM failure, justifying a long term PNH clone size monitoring, even in these patients.
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Le Garff-Tavernier:Alexion: Consultancy, Honoraria. Pruvot Debliquis:Alexion: Honoraria; Takeda: Honoraria; Pfizer: Honoraria; Gilead: Honoraria; Genzyme: Honoraria. Socie:Alexion: Consultancy. Peffault de Latour:Alexion: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Research Funding. Drenou:Alexion: Consultancy, Honoraria. Wagner Ballon:Alexion: Consultancy, Honoraria.
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