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

Human leukocyte antigen-B27 typing by flow cytometry: Comparison of three CE-IVD methods

BACKGROUND

The human leukocyte antigen B27 (HLA-B27), associated with chronic inflammatory diseases is thus widely performed for diagnostic purposes. Genotyping by molecular biology is the current gold standard for HLA-B27 typing, but cheaper and faster flow cytometry methods have been developed.

METHODS

In this report, we compare analytical performances of three CE-IVD flow cytometry kits: IOTest™ and DuraClone B27™ from Beckman Coulter and BD HLA-B27™ from BD Biosciences on a Navios™ cytometer as compared to molecular biology.

RESULTS

Routine analyses could conclude for HLA-B27 in197 patients (23.2%) and was not conclusive for 66 patients (7%, 8%). The experience revealed the needs to complete IOTest™ with a lineage marker (like CD3-APC) and a standardization procedure in detection of fluorescence. Comparative analysis considering 23/44 non-conclusive samples as negative, pointed out a 100% sensitivity and specificity of IOTest™ in determining genetically proved HLA-B27. Specificity of the BD HLA-B27TM kit was 94% (two false positives) sticking to the manufacturer instructions but raised to 100% and 94% sensitivity with a cutoff at 8.5 (225 on FACSdiva's scale).

DISCUSSION

The DuraClone B27™ specificity was poor using the manufacturer cutoff but raised to 100% with a 8.0 cutoff instead of 15.

CONCLUSION

The three flow cytometry kits displayed satisfying performances but need adjustments. The DuraClone B27™ kit seems to be the best while the IOTest™ kit is not conclusive in 8% of cases. In most cases the use of molecular biology can be spared, but genotyping remains essential for patients whose HLA-B27 status cannot be determined with confidence by flow cytometry.

Inter-intra instrument comparison and standardization of a 10-color immunophenotyping for B and T cell non-Hodgkin lymphoma diagnosis and monitoring

Harmonization of flow cytometry protocols from instrument settings to antibody panel and reagents is highly encouraged for inter-laboratory data comparison in both research and clinical settings, especially for minimal residual disease monitoring evaluation in hematological diseases across centers. Here, we described inter-intra instrument comparison of two standardized 10-color staining dried tubes for B- and T-cell lymphoproliferative disorder diagnosis and monitoring on two different flow cytometers, a Beckman Coulter NaviosEx and a Beckman Coulter DxFlex. A total of 47 consecutive patients were enrolled, and 39 of them were evaluable for further studies. We show highly comparable results between the two cytometers for cell frequency and fluorescence intensity signals for both standardized 10-color staining dried tubes. For this latter, fluorescence of each antibody and subject was normalized on the mean value obtained from the entire study cohort thus reducing the effects of biological variability and allowing comparison between instruments with different detector sensitivity. In summary, dried tubes were confirmed as an optimal standardized diagnostic tool, especially when associated with EuroFlow standardized procedures by minimizing technical and biological variability. However, data analysis is still operator-dependent, and more efforts are needed to develop automated or semi-automated software for flow cytometry data analysis for diagnostic purposes.

Flow cytometric method transfer: Recommendations for best practice

As with many aspects of the validation and monitoring of flow cytometric methods, the method transfer processes and acceptance criteria described for other technologies are not fully applicable. This is due to the complexity of the highly configurable instrumentation, the complexity of cellular measurands, the lack of qualified reference materials for most assays, and limited specimen stability. There are multiple reasons for initiating a method transfer, multiple regulatory settings, and multiple context of use. All of these factors influence the specific requirements for the method transfer. This recommendation paper describes the considerations and best practices for the transfer of flow cytometric methods and provides individual case studies as examples. In addition, the manuscript emphasizes the importance of appropriately conducting a method transfer on data reliability.

International guidelines for the flow cytometric evaluation of peripheral blood for suspected Sézary syndrome or mycosis fungoides: Assay development/optimization, validation, and ongoing quality monitors

Introducing a sensitive and specific peripheral blood flow cytometric assay for Sézary syndrome and mycosis fungoides (SS/MF) requires careful selection of assay design characteristics, and translation into a laboratory developed assay through development/optimization, validation, and continual quality monitoring. As outlined in a previous article in this series, the recommended design characteristics of this assay include at a minimum, evaluation of CD7, CD3, CD4, CD8, CD26, and CD45, analyzed simultaneously, requiring at least a 6 color flow cytometry system, with both quantitative and qualitative components. This article provides guidance from an international group of cytometry specialists in implementing an assay to those design specifications, outlining specific considerations, and best practices. Key points presented in detail are: (a) Pre-analytic components (reagents, specimen processing, and acquisition) must be optimized to: (i) identify and characterize an abnormal population of T-cells (qualitative component) and (ii) quantitate the abnormal population (semi/quasi-quantitative component). (b)Analytic components (instrument set-up/acquisition/analysis strategy and interpretation) must be optimized for the identification of SS/MF populations, which can vary widely in phenotype. Comparison with expert laboratories is strongly encouraged in order to establish competency. (c) Assay performance must be validated and documented through a validation plan and report, which covers both qualitative and semi/quasi-quantitative assay components (example template provided). (d) Ongoing assay-specific quality monitoring should be performed to ensure consistency.

Monocyte subsets to differentiate chronic myelomonocytic leukemia from reactive monocytosis

Background

Chronic myelomonocytic leukemia (CMML) is characterized by persistent monocytosis and dysplastic features of blood cells. No specific genetic abnormalities are present in CMML, and reactive monocytosis should be excluded. An increase in classical monocytes (MO1) has been suggested as a screening tool for CMML.

Methods

We evaluated monocyte subsets in the peripheral blood of patients with CMML (n = 16), patients with reactive monocytosis (n = 19), and normal controls (n = 15) with flow cytometry using antibodies against CD14, CD16, CD56, CD24, CD45, and CD2. The cutoff of MO1 ≥94% was validated, and the optimal cutoff was analyzed with receiver operating curve analysis.

Results

The sensitivity of monocyte subset testing for screening for CMML was 0.938 (0.717‐0.997), and the specificity was 0.882 (0.734 ‐ 0.953) using the cutoff of MO1 ≥94%. Serial samples from patients who responded to hypomethylating therapy showed an MO1 < 94%. However, few patients with reactive monocytosis, including patients with nonhematologic malignancies and acute myeloid leukemia, showed an increase in the MO1 ≥ 94%. Monocyte subset results were correlated with the response to hypomethylating therapy in follow‐up samples.

Conclusion

Monocyte subset analysis is useful in screening for and monitoring CMML. Harmonization of the protocols for monocyte subset analysis is required.

Multicentric MFI30 study: Standardization of flow cytometry analysis of CD30 expression in non-Hodgkin lymphoma

CD30 transmembrane receptor, a member of the tumor necrosis factor receptor family, is expressed in different lymphomas. Brentuximab vedotin (BV), a CD30 monoclonal antibody (Ab)-drug conjugate, is effective in CD30-positive lymphomas. However, the response to BV is not always correlated to CD30 expression detected by immunohistochemistry (IHC). The objectives of this study were to standardize and evaluate CD30 intensity by flow cytometry (FCM) in non-Hodgkin's lymphomas. Twelve centers analyzed 161 cases on standardized cytometers using normalized median fluorescence intensity (nMFI30) of three different Abs, of which one clone can recognize the same epitope as BV. FCM distinguished four groups of cases: negative group (n = 110) which showed no expression with the three clones; high positive group (n = 13) which gave nMFI30 > 5% with all tested clones; dim positive group (n = 17) which showed nMFI30 > 1% with all tested clones and <5% for at least one; discordant group (n = 21) with positive and negative expression of the different clones. In consistency with the literature, CD30 was positive in all anaplastic large cell lymphomas, in some diffuse large B-cell lymphomas (DLBCL), and in other rare lymphomas. FCM results were concordant with those of IHC in 77% of cases. Discrepancies could be explained by clones-related differences, microenvironment, or intracytoplasmic staining. Interestingly, FCM was more sensitive than IHC in 11% of cases, especially in DLBCL. Multicenter standardized FCM of specific CD30 could improve case detection and extend the treatment of BV to various CD30-positive lymphomas.

Standardization procedure for flow cytometry data harmonization in prospective multicenter studies

One of the most challenging objective for clinical cytometry in prospective multicenter immunomonitoring trials is to compare frequencies, absolute numbers of leukocyte populations and further the mean fluorescence intensities of cell markers, especially when the data are generated from different instruments. Here, we describe an innovative standardization workflow to compare all data to carry out any large-scale, prospective multicentric flow cytometry analysis whatever the duration, the number or type of instruments required for the realization of such projects.

FACSCanto II and LSRFortessa flow cytometer instruments can be synchronized utilizing single-fluorochrome-conjugated surface-dyed beads for standardized immunophenotyping

Background

Multiparameter flow cytometry is the preferred method to determine immunophenotypic features of cells present in a wide variety of sample types. Standardization is key to avoid inconsistencies and subjectivity of interpretations between clinical diagnostic laboratories. Among these standardization requirements, synchronization between different flow cytometer instruments is indispensable to obtain comparable results. This study aimed to investigate whether two widely used flow cytometers, the FACSCanto II and LSRFortessa, can be effectively synchronized utilizing calibration bead–based synchronization.

Method

Two FACSCanto II and two LSRFortessa flow cytometers were synchronized with both multicolor hard‐dyed and single‐fluorochrome–conjugated surface‐dyed beads according to the manufacturer's instructions. Cell staining was performed on five whole‐blood samples obtained from healthy controls and were analyzed upon synchronization with the respective synchronization protocols.

Results

Comparability criteria (defined as <15% deviation from the reference instrument) were met with both bead sets when synchronizing different FACSCanto II or LSRFortessa instruments. However, we observed that the criteria could not be met when synchronizing FACSCanto II with LSRFortessa instruments with multicolor hard‐dyed beads. By utilizing single‐fluorochrome–conjugated surface‐dyed beads to determine and adjust PMT voltages, the accepted comparability criteria were successfully met. The protocol has been validated using five different eight‐parameter stained samples.

Conclusion

We show that FACSCanto II and LSRFortessa instruments can effectively be synchronized using single‐fluorochrome–conjugated surface‐dyed beads in case deviation criteria cannot be met using multicolor hard‐dyed beads. Synchronization with single‐fluorochrome–conjugated surface‐dyed beads results in decreased deviations between instruments, allowing comparability criteria to become stricter.

Multicentre Harmonisation of a Six-Colour Flow Cytometry Panel for Naïve/Memory T Cell Immunomonitoring

Background

Personalised medicine in oncology needs standardised immunological assays. Flow cytometry (FCM) methods represent an essential tool for immunomonitoring, and their harmonisation is crucial to obtain comparable data in multicentre clinical trials. The objective of this study was to design a harmonisation workflow able to address the most effective issues contributing to intra- and interoperator variabilities in a multicentre project.

Methods

The Italian National Institute of Health (Istituto Superiore di Sanità, ISS) managed a multiparametric flow cytometric panel harmonisation among thirteen operators belonging to five clinical and research centres of Lazio region (Italy). The panel was based on a backbone mixture of dried antibodies (anti-CD3, anti-CD4, anti-CD8, anti-CD45RA, and anti-CCR7) to detect naïve/memory T cells, recognised as potential prognostic/predictive immunological biomarkers in cancer immunotherapies. The coordinating centre distributed frozen peripheral blood mononuclear cells (PBMCs) and fresh whole blood (WB) samples from healthy donors, reagents, and Standard Operating Procedures (SOPs) to participants who performed experiments by their own equipment, in order to mimic a real-life scenario. Operators returned raw and locally analysed data to ISS for central analysis and statistical elaboration.

Results

Harmonised and reproducible results were obtained by sharing experimental set-up and procedures along with centralising data analysis, leading to a reduction of cross-centre variability for naïve/memory subset frequencies particularly in the whole blood setting.

Conclusion

Our experimental and analytical working process proved to be suitable for the harmonisation of FCM assays in a multicentre setting, where high-quality data are required to evaluate potential immunological markers, which may contribute to select better therapeutic options.

Standardization of Flow Cytometric Immunophenotyping for Hematological Malignancies: The FranceFlow Group Experience

Flow cytometry is broadly used for the identification, characterization, and monitoring of hematological malignancies. However, the use of clinical flow cytometry is restricted by its lack of reproducibility across multiple centers. Since 2006, the EuroFlow consortium has been developing a standardized procedure detailing the whole process from instrument settings to data analysis. The FranceFlow group was created in 2010 with the intention to educate participating centers in France about the standardized instrument setting protocol (SOP) developed by the EuroFlow consortium and to organise several rounds of quality controls (QCs) in order to evaluate the feasibility of its application and its results. Here, we report the 5 year experience of the FranceFlow group and the results of the seven QCs of 23 instruments, involving up to 19 centers, in France and in Belgium. The FranceFlow group demonstrates that both the distribution and applicability of the SOP have been successful. Intercenter reproducibility was evaluated using both normal and pathological blood samples. Coefficients of variation (CVs) across the centers were <7% for the percentages of cell subsets and <30% for the median fluorescence intensities (MFIs) of the markers tested. Intracenter reproducibility provided similar results with CVs of <3% for the percentages of the majority of cell subsets, and CVs of <20% for the MFI values for the majority of markers. Altogether, the FranceFlow group show that the 19 participating labs might be considered as one unique laboratory with 23 identical flow cytometers able to reproduce identical results. Therefore, SOP significantly improves reproducibility of clinical flow in hematology and opens new avenues by providing a robust companion diagnostic tool for clinical trials in hematology. © 2019 International Society for Advancement of Cytometry.

Flow cytometric analysis of neutrophil myeloperoxidase expression in peripheral blood for ruling out myelodysplastic syndromes: a diagnostic accuracy study

Suspicion of myelodysplastic syndromes (MDS) is one of the commonest reasons for bone marrow aspirate in elderly patients presenting with persistent peripheral blood (PB) cytopenia of unclear etiology. A PB assay that accurately rules out MDS would have major benefits. The diagnostic accuracy of the intra-individual robust coefficient of variation (RCV) for neutrophil myeloperoxidase (MPO) expression measured by flow cytometric analysis in PB was evaluated in a retrospective derivation study (44 MDS cases and 44 controls) and a prospective validation study (68 consecutive patients with suspected MDS). Compared with controls, MDS cases had higher median RCV values for neutrophil MPO expression (40.2% vs. 30.9%; P<0.001). The area under the receiver operating characteristic curve estimates were 0.94 [95% confidence interval (CI): 0.86-0.97] and 0.87 (95%CI: 0.76-0.94) in the derivation and validation studies, respectively. A RCV lower than 30% ruled out MDS with 100% sensitivity (95%CI: 78-100%) and 100% negative predictive value (95%CI: 83-100%) in the prospective validation study. Neutrophil MPO expression measured by flow cytometric analysis in PB might obviate the need for invasive bone marrow aspirate and biopsy for up to 29% of patients with suspected MDS.

How Clinical Flow Cytometry Rebooted Sepsis Immunology

On May 2017, the World Health Organization (WHO) recognized sepsis as a global health priority by adopting a resolution to improve the prevention, diagnosis, and management of this deadly disease. While it has long been known that sepsis deeply perturbs immune homeostasis by inducing a tremendous systemic inflammatory response, pivotal observations based on clinical flow cytometry indicate that sepsis indeed initiates a more complex immune response that varies over time, with the concomitant occurrence of both pro- and anti-inflammatory mechanisms. As a resultant, some septic patients enter a stage of protracted immunosuppression. This paved the way for immunostimulation approaches in sepsis. Clinical flow cytometry permitted this evolution by drawing a new picture of pathophysiology and reshaping immune trajectories in patients. Additional information from cytometry by time of flight mass cytometry and other high-dimensional flow cytometry platform should rapidly enrich our understanding of this complex disease. This review reports on landmarks of clinical flow cytometry in sepsis and how this single-cell analysis technique permitted to breach the wall of decades of unfruitful anti-inflammatory-based clinical trials in sepsis. © 2019 International Society for Advancement of Cytometry.

Multicentric Standardized Flow Cytometry Routine Assessment of Patients With Sepsis to Predict Clinical Worsening

BACKGROUND

In this study, we primarily sought to assess the ability of flow cytometry to predict early clinical deterioration and overall survival in patients with sepsis admitted in the ED and ICU.

METHODS

Patients admitted for community-acquired acute sepsis from 11 hospital centers were eligible. Early (day 7) and late (day 28) deaths were notified. Levels of CD64^pos granulocytes, CD16^pos monocytes, CD16^dim immature granulocytes (IGs), and T and B lymphocytes were assessed by flow cytometry using an identical, cross-validated, robust, and simple consensus standardized protocol in each center.

RESULTS

Among 1,062 patients screened, 781 patients with confirmed sepsis were studied (age, 67 ± 48 years; Simplified Acute Physiology Score II, 36 ± 17; Sequential Organ Failure Assessment, 5 ± 4). Patients were divided into three groups (sepsis, severe sepsis, and septic shock) on day 0 and on day 2. On day 0, patients with sepsis exhibited increased levels of CD64^pos granulocytes, CD16^pos monocytes, and IGs with T-cell lymphopenia. Clinical severity was associated with higher percentages of IGs and deeper T-cell lymphopenia. IG percentages tended to be higher in patients whose clinical status worsened on day 2 (35.1 ± 35.6 vs 43.5 ± 35.2, P = .07). Increased IG percentages were also related to occurrence of new organ failures on day 2. Increased IG percentages, especially when associated with T-cell lymphopenia, were independently associated with early (P < .01) and late (P < .01) death.

CONCLUSIONS

Increased circulating IGs at the acute phase of sepsis are linked to clinical worsening, especially when associated with T-cell lymphopenia. Early flow cytometry could help clinicians to target patients at high risk of clinical deterioration.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01995448; URL: www.clinicaltrials.gov.

How to make usage of the standardized EuroFlow 8-color protocols possible for instruments of different manufacturers

A critical component of the EuroFlow standardization of leukemia/lymphoma immunophenotyping is instrument setup. Initially, the EuroFlow consortium developed a step-by-step standard operating protocol for instrument setup of ≥8-color flow cytometers that were available in 2006, when the EuroFlow activities started. Currently, there are 14 instruments from 9 manufacturers capable of 3-laser excitation and ≥8 color measurements. The specific adaptations required in the instrument set-up to enable them to acquire the standardized 8-color EuroFlow protocols are described here. Overall, all 14 instruments can be fitted with similar violet, blue and red lasers for simultaneous measurements of ≥8 fluorescent dyes. Since individual instruments differ both on their dynamic range (scale) and emission filters, it is not accurate to simply recalculate the target values to different scale, but adjustment of PMT voltages to a given emission filter and fluorochrome, is essential. For this purpose, EuroFlow has developed an approach using Type IIB (spectrally matching) particles to set-up standardized and fully comparable fluorescence measurements, in instruments from different manufacturers, as demonstrated here for the FACSCanto II, and Navios and MACSQuant flow cytometers. Data acquired after such adjustment on any of the tested cytometry platforms could be fully superimposed and therefore analyzed together. The proposed approach can be used to derive target values for any combination of spectrally distinct fluorochromes and any distinct emission filter of any new flow cytometry platform, which enables the measurement of the 8-color EuroFlow panels in a standardized way, by creating superimposable datafiles.

High-resolution phenotyping identifies NK cell subsets that distinguish healthy children from adults

Natural killer (NK) cells are critical in immune defense against infected, stressed or transformed cells. Their function is regulated by the heterogeneous expression of a wide array of surface receptors that shape its phenotypic diversity. Although NK cells develop in the bone marrow and secondary lymphoid tissues, substantive differentiation is apparent in the peripheral blood including known age-related variation. In order to gain greater insight into phenotypic and functional variation within peripheral blood NK cells across age groups, we used multi-parametric, polyfunctional flow cytometry to interrogate the NK cell variability in 20 healthy adults and 15 5–10, 11–15 and 16–20 year-old children. We found that the normative ranges in both adults and children displayed great inter-individual variation for most markers. While the expression of several receptors did not differ, among those that did, the majority of the differences existed between adults and the three pediatric groups, rather than among children of different ages. Interestingly, we also identified variation in the individual expression of some markers by sex and ethnicity. Combinatorial analysis of NK cell receptors revealed intermediate subsets between the CD56^bright and CD56^dim NK cells. Furthermore, on examining the NK cell diversity by age, adults were discovered to have the lowest developmental diversity. Thus, our findings identify previously unappreciated NK cell subsets potentially distinguishing children from adults and suggest functional correlates that may have relevance in age-specific host defense.

Standardization of 8-color flow cytometry across different flow cytometer instruments: A feasibility study in clinical laboratories in Switzerland

The EuroFlow Consortium developed a fully standardized flow cytometric approach from instrument settings, through antibody panel, reagents and sample preparation protocols, to data acquisition and analysis. The Swiss Cytometry Society (SCS) promoted a study to evaluate the feasibility of using such standardized measurements of 8-color data across two different flow cytometry platforms - Becton Dickinson (BD) FACSCanto II and Beckman Coulter (BC) Navios, aiming at increasing reproducibility and inter-laboratory comparability of immunophenotypic data in clinical laboratories in Switzerland. The study was performed in two phases, i.e. a learning phase (round 1) and an analytical phase (rounds 2 and 3) consisting of a total of three rounds. Overall, 10 laboratories using BD FACSCanto II (n=6) or BC Navios (n=4) flow cytometers participated. Each laboratory measured peripheral blood samples from healthy donors stained with a uniform antibody panel of reagents - EuroFlow Lymphoid Screening Tube (LST) - applying the EuroFlow standardized protocols for instrument setup and sample preparation (www.EuroFlow.org). All data files were analyzed centrally and median fluorescence intensity (MedFI) values for individual markers on defined lymphocyte subsets were recorded; variability from reference MedFI values was assessed using performance scores. Data troubleshooting and discussion of the results with the participants followed after each round at SCS meetings. The results of the learning phase demonstrated that standardized instrument setup and data acquisition are feasible in routine clinical laboratories without previous experience with EuroFlow. During the analytical phase, highly comparable data were obtained at the different laboratories using either BD FACSCanto II or BC Navios. The coefficient of variation of MedFI for 7 of 11 markers performed repeatedly below 30%. In the last study round, 89% of participants scored over 90% MedFI values within the acceptance criteria (P-score), in line with the results of the EuroFlow quality assessment rounds performed by the EuroFlow expert laboratories(Kalina et al., 2015). Central analysis of data allowed identification of deviations from the standardized procedures and technical issues (e.g. failure to perform correct instrument setup and improper compensation). In summary, here we show that inter-laboratory cross-platform standardization of 8-color flow cytometric measurements in clinical laboratories is feasible and allows for fully comparable MedFI results across BD FACSCanto II and BC Navios instruments. However, adherence to standardized protocols is crucial. Thus, training of the laboratory personnel in the EuroFlow standardized procedures is highly recommended to prevent errors in instrument setup and sample preparation.

One tube with eight antibodies for 14-part bone marrow leukocyte differential using flow cytometry

BACKGROUND

Bone marrow analysis by flow cytometry is part of the routine diagnosis of hematological disorders in medical laboratories. Differential leukocyte count and identification of abnormal cell subsets is currently performed through morphological examination on bone marrow smears by skilled cytologists. In this work, we propose a single 8-color tube for providing equivalent information, using flow cytometry.

METHODS

99 bone marrow samples were classified into 2 groups, (i) 51 samples, obtained from either healthy donors (n = 4) or patients with various diseases at diagnosis or during remission that did not present a hematological malignancy (n = 47), and (ii) 48 pathological samples with quantitative and/or qualitative abnormalities. A panel of eight antibodies-CD3-FITC/CD10-PE/CD38-PerCP-Cy5.5/CD19-PECy7/CD36-APC/CD16-APC-H7/CD34-BV421/CD45-V500-was tested to identify the main cell subsets at different stages of maturation using a FACSCanto-II analyzer.

RESULTS

We first proposed a strategy of sequential gating leading to the identification of 14 leukocyte subsets, that is, erythroblasts, monocytes, B-lymphoid cells from hematogones to plasma-cells (5 subsets), T- and NK-cells, polymorphonuclear cells (neutrophils, eosinophils, and basophils), myeloblasts and other immature granular cells. This approach was validated by comparing flow cytometry and microscopic morphological examination, both in cases of normal and abnormal samples. Interestingly, cell identification, and numeration by flow cytometry was easy to perform and highly reproducible.

CONCLUSION

A very simple, rapid, and reproducible flow cytometric approach, using a combination of eight antibodies allows determination of the cellular composition of bone marrow with high precision. © 2016 International Clinical Cytometry Society.

CD180 expression in B-cell lymphomas: A multicenter GEIL study

CD180, a related member of the Toll-like receptor family, is lost or underexpressed at the plasma membrane in circulating cells of various B-cell lymphomas except marginal zone lymphomas (MZL). In order to confirm its clinical relevance in routine analysis, we evaluated prospectively the expression of CD180 in 236 patients from 5 French University Hospital laboratories on behalf of the GEIL. Highly comparable results were obtained in all centers using the EuroFlow standardization protocol. We observed that CD180 median fluorescence (MdFI) was significantly higher in MZL and hairy cell leukaemia (HCL) compared to all other B-cell proliferations (P < 0.05). CD180 intensity could distinguish lymphomas with numerous villous lymphocytes from other MZL. ROC curve analysis identified a CD180 MdFI threshold for which the diagnosis of MZL could be assessed with 77% sensitivity and 92% specificity. This study showed that CD180 can be considered as a single positive robust marker of MZL and should be therefore included in flow cytometry panels for the diagnosis of mature B-cell neoplasms. Harmonization process is of great interest in order to evaluate new markers in multicentric studies and to set up decisional thresholds. © 2015 International Clinical Cytometry Society.

Fifteen years of external quality assessment in leukemia/lymphoma immunophenotyping in The Netherlands and Belgium: A way forward

In 1985, external quality assurance was initiated in the Netherlands to reduce the between-laboratory variability of leukemia/lymphoma immunophenotyping and to improve diagnostic conclusions. This program consisted of regular distributions of test samples followed by biannual plenary participant meetings in which results were presented and discussed. A scoring system was developed in which the quality of results was rated by systematically reviewing the pre-analytical, analytical, and post-analytical assay stages using three scores, i.e., correct (A), minor fault (B), and major fault (C). Here, we report on 90 consecutive samples distributed to 40-61 participating laboratories between 1998 and 2012. Most samples contained >20% aberrant cells, mainly selected from mature lymphoid malignancies (B or T cell) and acute leukemias (myeloid or lymphoblastic). In 2002, minimally required monoclonal antibody (mAb) panels were introduced, whilst methodological guidelines for all three assay stages were implemented. Retrospectively, we divided the study into subsequent periods of 4 ("initial"), 4 ("learning"), and 7 years ("consolidation") to detect "learning effects." Uni- and multivariate models showed that analytical performance declined since 2002, but that post-analytical performance improved during the entire period. These results emphasized the need to improve technical aspects of the assay, and reflected improved interpretational skills of the participants. A strong effect of participant affiliation in all three assay stages was observed: laboratories in academic and large peripheral hospitals performed significantly better than those in small hospitals. © 2015 International Clinical Cytometry Society.