Julien Guy

Immunologic effects of rituximab on the human spleen in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease with a complex pathogenesis. As in many B cell-related autoimmune diseases, rituximab (RTX) has been shown to increase platelet counts in some ITP patients. From an immunologic standpoint, the mode of action of RTX and the reasons underlying its limited efficacy have yet to be elucidated. Because splenectomy is a cornerstone treatment of ITP, the immune effect of RTX on this major secondary lymphoid organ was investigated in 18 spleens removed from ITP patients who were treated or not with RTX. Spleens from ITP individuals had follicular hyperplasia consistent with secondary follicles. RTX therapy resulted in complete B-cell depletion in the blood and a significant reduction in splenic B cells, but these patients did not achieve remission. Moreover, whereas the percentage of circulating regulatory T cells (Tregs) was similar to that in controls, splenic Tregs were reduced in ITP patients. Interestingly, the ratio of proinflammatory Th1 cells to suppressive Tregs was increased in the spleens of patients who failed RTX therapy. These results indicate that although B cells are involved in ITP pathogenesis, RTX-induced total B-cell depletion is not correlated with its therapeutic effects, which suggests additional immune-mediated mechanisms of action of this drug.

Clinical features and course of refractory anemia with ring sideroblasts associated with marked thrombocytosis

Background Refractory anemia with ring sideroblasts associated with marked thrombocytosis was proposed as a provisional entity in the 2001 World Health Organization classification of myeloid neoplasms and also in the 2008 version, but its existence as a single entity is contested. We wish to define the clinical features of this rare myelodysplastic/myeloproliferative neoplasm and to compare its clinical outcome with that of refractory anemia with ring sideroblasts and essential thrombocythemia. Design and Methods We conducted a collaborative retrospective study across Europe. Our database included 200 patients diagnosed with refractory anemia with ring sideroblasts and marked thrombocytosis. For each of these patients, each patient diagnosed with refractory anemia with ring sideroblasts was matched for age and sex. At the same time, a cohort of 454 patients with essential thrombocythemia was used to compare outcomes of the two diseases. Results In patients with refractory anemia with ring sideroblasts and marked thrombocytosis, depending on the Janus Kinase 2 V617F mutational status (positive or negative) or platelet threshold (over or below 600×109/L), no difference in survival was noted. However, these patients had shorter overall survival and leukemia-free survival with a lower risk of thrombotic complications than did patients with essential thrombocythemia (P<0.001) but better survival (P<0.001) and a higher risk of thrombosis (P=0.039) than patients with refractory anemia with ring sideroblasts. Conclusions The clinical course of refractory anemia with ring sideroblasts and marked thrombocytosis is better than that of refractory anemia with ring sideroblasts and worse than that of essential thrombocythemia. The higher risk of thrombotic events in this disorder suggests that anti-platelet therapy might be considered in this subset of patients. From a clinical point of view, it appears to be important to consider refractory anemia with ring sideroblasts and marked thrombocytosis as a distinct entity.

Comparable flow cytometry data can be obtained with two types of instruments, Canto II, and Navios. A GEIL study.

Flow cytometry (FC) instruments settings classically rely on local establishment of photomultipliers (PMT) voltages adapted to the measurements expected to be performed. In the era of multiparameter FC (MFC), it appears more and more desirable that comparable patterns of fluorescence are obtained in different settings. This relies on a harmonization of settings between instruments. Although this has been shown to be feasible within a given brand of flow cytometers, little information is available about broader comparisons in a given center or in a multicenter fashion. Here, we report a two‐phase series of experiments first performed between a Canto II (BD Biosciences) and a Navios (Beckman Coulter) instruments in the same center. PMT values adjusted on the reference instrument (RI) Canto II were used to establish target values for PMT settings on the paired Navios practice instrument (PI). This allowed to show the good correlation of all but peaks 1 and 2 of Rainbow® beads between RI and PI. Using 4‐ or 8‐color stained leukocytes, the similitude of the settings was further confirmed. A complex set of matrices was then established between five centers all equipped with both instruments. Using Bland & Altman difference comparisons for median fluorescence values, it was shown that using either Rainbow beads or CD16 stained polymorphonuclears to set‐up target values on the RI CantoII, highly superimposable results could be obtained on all 9 PI. The latter were obtained using Rainbow beads or Compbeads® for comparisons. In summary, this two‐phase study demonstrates the feasibility of different methods allowing for a robust harmonization of settings for MFC.

A GEIL flow cytometry consensus proposal for quantification of plasma cells: application to differential diagnosis between MGUS and myeloma.

Flow cytometry is the sole available technique for quantification of tumor plasma‐cells in plasma‐cell disorders, but so far, no consensus technique has been proposed. Here, we report on a standardized, simple, robust five color flow cytometry protocol developed to characterize and quantify bone marrow tumor plasma‐cells, validated in a multicenter manner.

The level of blast CD33 expression positively impacts the effect of gemtuzumab ozogamicin in patients with acute myeloid leukemia

To the editor: Gemtuzumab ozogamicin (GO) is an immunoconjugate, combining an anti-CD33 monoclonal antibody to calicheamicin, a highly cytotoxic antibiotic. First developed as single agent in adults with relapsed acute myeloid leukemia (AML),[1][1] it was then evaluated in combination with

Flow cytometry thresholds of myeloperoxidase detection to discriminate between acute lymphoblastic or myeloblastic leukaemia

The World Health Organization 2008 Classification emphasizes myeloperoxidase (MPO) detection as sufficient for assigning a blast population to the myeloid lineage. Published MPO positivity thresholds are 10% for flow cytometry (FCM) but 3% for cytochemistry. Here we re‐evaluated the FCM‐MPO threshold by comparing retrospectively 128 acute lymphoblastic leukaemias and 75 acute myeloid leukaemias without maturation, all assessed by benzidine‐based cytochemistry. A 13% threshold was found to be relevant using an isotype control as background‐reference (sensitivity 95·1%, specificity 91·7%). Residual normal lymphocytes proved to be an advantageous alternative reference, a threshold of 28% yielding improved 97·4% sensitivity and 96·1% specificity.

Comparison of cross-platform flow cytometry minimal residual disease evaluation in multiple myeloma using a common antibody combination and analysis strategy.

A seven‐color/eight‐antibody approach has recently been proposed for the minimal residual disease (MRD) determination in multiple myeloma (MM), which was developed on FACSCantoII instruments. This strategy should be also applicable on different multiparameter flow cytometers (MFC), but this needs to be demonstrated before moving MRD assessment to local flow cytometry core facilities, nearer to patients, thereby reducing the risk of cell losses induced by sample transportation and delays in cell processing.

Multicentric study underlining the interest of adding CD5, CD7 and CD56 expression assessment to the flow cytometric Ogata score in myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms

Although numerous recent publications have demonstrated interest in multiparameter flow cytometry in the investigation of myelodysplastic disorders, it is perceived by many laboratory hematologists as difficult and expensive, requiring a high level of expertise. We report a multicentric open real-life study aimed at evaluating the added value of the technically simple flow cytometry score described by the Ogata group for the diagnosis of myelodysplastic syndromes. A total of 652 patients were recruited prospectively in four different centers: 346 myelodysplastic syndromes, 53 myelodysplastic/myeloproliferative neoplasms, and 253 controls. The Ogata score was assessed using CD45 and CD34 staining, with the addition of CD10 and CD19. Moreover, labeling of CD5, CD7 and CD56 for the evaluation of myeloid progenitors and monocytes was tested on a subset of 294 patients. On the whole series, the specificity of Ogata score reached 89%. Respective sensitivities were 54% for low-risk myelodysplastic syndromes, 68% and 84% for type 1 and type 2 refractory anemia with excess of blasts, and 72% for myelodysplastic/myeloproliferative neoplasms. CD5 expression was poorly informative. When adding CD56 or CD7 labeling to the Ogata score, sensitivity rose to 66% for low-risk myelodysplastic syndromes, to 89% for myelodysplastic/myeloproliferative neoplasms and to 97% for refractory anemia with excess of blasts. This large multicenter study confirms the feasibility of Ogata scoring in routine flow cytometry diagnosis but highlights its poor sensitivity in low-risk myelodysplastic syndromes. The addition of CD7 and CD56 in flow cytometry panels improves the sensitivity but more sophisticated panels would be more informative.

Calreticulin Mutations in Myeloproliferative Neoplasms: Comparison of Three Diagnostic Methods

Calreticulin (CALR) mutations have recently been reported in 70–84% of JAK2V617F-negative myeloproliferative neoplasms (MPN), and this detection has become necessary to improve the diagnosis of MPN. In a large single-centre cohort of 298 patients suffering from Essential Thrombocythemia (ET), the JAK2V617F, CALR and MPL mutations were noted in 179 (60%), 56 (18.5%) and 13 (4.5%) respectively. For the detection of the CALR mutations, three methods were compared in parallel: high-resolution melting-curve analysis (HRM), product-sizing analysis and Sanger sequencing. The sensitivity for the HRM, product-sizing analysis and Sanger sequencing was 96.4%, 98.2% and 89.3% respectively, whereas the specificity was 96.3%, 100% and 100%. In our cohort, the product-sizing analysis was the most sensitive method and was the easiest to interpret, while the HRM was sometimes difficult to interpret. In contrast, when large series of samples were tested, HRM provided results more quickly than did the other methods, which required more time. Finally, the sequencing method, which is the reference method, had the lowest sensitivity but can be used to describe the type of mutation precisely. Altogether, our results suggest that in routine laboratory practice, product-sizing analysis is globally similar to HRM for the detection of CALR mutations, and that both may be used as first-line screening tests. If the results are positive, Sanger sequencing can be used to confirm the mutation and to determine its type. Product-sizing analysis provides sensitive and specific results, moreover, with the quantitative measurement of CALR, which might be useful to monitor specific treatments.

Flow cytometry test for hereditary spherocytosis

We read with interest the recent article of Bianchi et al . published in Haematologica that compared laboratory tests for hereditary spherocytosis (HS) in 150 patients.[1][1] The authors reported the usefulness of the eosine-5-maleimide binding (EMA) test in the diagnosis of HS with high sensitivity