Explore the vast range of titles available.

Key Points Standardized immunophenotyping assays are a requisite for accomplishing the proposed Human Immunology Project, which involves the comprehensive elucidation of the metrics of healthy versus diseased or perturbed human immune systems. The variables inherent in flow cytometry immunophenotyping are largely known, and include reagent choice, sample handling, instrument setup and data analysis; strategies to mitigate each of these variables are available. Several groups, including the Human Immunophenotyping Consortium, are standardizing reagent panels for flow cytometry. Together with the adoption of such standard panels, an infrastructure for aggregating and mining results will be needed. Availability of such panels and the data-mining infrastructure should result in more rapid biomarker discovery for immunologically relevant diseases. The authors use flow cytometry of peripheral blood mononuclear cells as an example to outline the approaches to assay standardization that will be required to realize the full potential of immunophenotyping as a research tool and in the clinic. The heterogeneity in the healthy human immune system, and the immunological changes that portend various diseases, have been only partially described. Their comprehensive elucidation has been termed the 'Human Immunology Project'. The accurate measurement of variations in the human immune system requires precise and standardized assays to distinguish true biological changes from technical artefacts. Thus, to be successful, the Human Immunology Project will require standardized assays for immunophenotyping humans in health and disease. A major tool in this effort is flow cytometry, which remains highly variable with regard to sample handling, reagents, instrument setup and data analysis. In this Review, we outline the current state of standardization of flow cytometry assays and summarize the steps that are required to enable the Human Immunology Project.

Standardization of immunophenotyping requires careful attention to reagents, sample handling, instrument setup, and data analysis, and is essential for successful cross-study and cross-center comparison of data. Experts developed five standardized, eight-color panels for identification of major immune cell subsets in peripheral blood. These were produced as pre-configured, lyophilized, reagents in 96-well plates. We present the results of a coordinated analysis of samples across nine laboratories using these panels with standardized operating procedures (SOPs). Manual gating was performed by each site and by a central site. Automated gating algorithms were developed and tested by the FlowCAP consortium. Centralized manual gating can reduce cross-center variability, and we sought to determine whether automated methods could streamline and standardize the analysis. Within-site variability was low in all experiments, but cross-site variability was lower when central analysis was performed in comparison with site-specific analysis. It was also lower for clearly defined cell subsets than those based on dim markers and for rare populations. Automated gating was able to match the performance of central manual analysis for all tested panels, exhibiting little to no bias and comparable variability. Standardized staining, data collection, and automated gating can increase power, reduce variability, and streamline analysis for immunophenotyping.

The EU-supported EuroFlow Consortium aimed at innovation and standardization of immunophenotyping for diagnosis and classification of hematological malignancies by introducing 8-color flow cytometry with fully standardized laboratory procedures and antibody panels in order to achieve maximally comparable results among different laboratories. This required the selection of optimal combinations of compatible fluorochromes and the design and evaluation of adequate standard operating procedures (SOPs) for instrument setup, fluorescence compensation and sample preparation. Additionally, we developed software tools for the evaluation of individual antibody reagents and antibody panels. Each section describes what has been evaluated experimentally versus adopted based on existing data and experience. Multicentric evaluation demonstrated high levels of reproducibility based on strict implementation of the EuroFlow SOPs and antibody panels. Overall, the 6 years of extensive collaborative experiments and the analysis of hundreds of cell samples of patients and healthy controls in the EuroFlow centers have provided for the first time laboratory protocols and software tools for fully standardized 8-color flow cytometric immunophenotyping of normal and malignant leukocytes in bone marrow and blood; this has yielded highly comparable data sets, which can be integrated in a single database.

Most consensus leukemia & lymphoma antibody panels consist of lists of markers based on expert opinions, but they have not been validated. Here we present the validated EuroFlow 8-color antibody panels for immunophenotyping of hematological malignancies. The single-tube screening panels and multi-tube classification panels fit into the EuroFlow diagnostic algorithm with entries defined by clinical and laboratory parameters. The panels were constructed in 2–7 sequential design–evaluation–redesign rounds, using novel Infinicyt software tools for multivariate data analysis. Two groups of markers are combined in each 8-color tube: (i) backbone markers to identify distinct cell populations in a sample, and (ii) markers for characterization of specific cell populations. In multi-tube panels, the backbone markers were optimally placed at the same fluorochrome position in every tube, to provide identical multidimensional localization of the target cell population(s). The characterization markers were positioned according to the diagnostic utility of the combined markers. Each proposed antibody combination was tested against reference databases of normal and malignant cells from healthy subjects and WHO-based disease entities, respectively. The EuroFlow studies resulted in validated and flexible 8-color antibody panels for multidimensional identification and characterization of normal and aberrant cells, optimally suited for immunophenotypic screening and classification of hematological malignancies.

Flow cytometric immunophenotyping of lymphocytes and dendritic cells, and functional lymphocyte mitogen response tests are used in the diagnostics of inborn errors of immunity (IEI), especially in pediatrics. These routinely used tests lack sufficient age-matched reference values in children. We established reference values for lymphocyte and dendritic cell subsets for four age groups from 68 healthy children under 12 years of age. These values were then compared to prior publicly available articles and 46 clinical samples from children with confirmed IEI diagnosis. Mitogen response results were also compared between 27 children and 177 adults. In the literature review, we found considerable variability in lymphocyte subset definitions and statistical approaches. Most IEI patients had increased transitional and naïve B, and decreased memory B cells. CHH patients had increased γδ T and DNTs. Lymphocyte stimulation via FASCIA method provides weaker stimulation results in children than in adults, which seems to result from a larger proportional count of naïve lymphocytes in children. The established reference values can be used in diagnostics of pediatric immunological conditions in laboratories that use similar analytic methods. Lower lymphocyte mitogen response results in children need to be taken into consideration when interpreting the results of lymphocyte functional tests.

Flow cytometry immunophenotypic analysis plays an important role in the diagnosis, classification, and disease monitoring of hematologic neoplasms. The interpretation of flow cytometry testing can be challenging. To explore ways to improve diagnostic accuracy and in turn enhance the quality of patient care. A flow cytometry quality assurance (QA) program was developed. Cases from various complex flow cytometry panels were randomly selected and cross-reviewed. The outcomes of the QA review were categorized into 3 groups: complete agreement, minor discrepancy, and major discrepancy. Each discrepancy underwent a process of documentation, discussion, and resolution. Here we summarize our 3 years of experience with this program. In total, 6166 cases were evaluated; 6028 cases (97.7%) showed complete concordance, 120 cases (2.0%) showed minor discrepancies, and 18 cases (0.3%) showed major discrepancies. Among the top 5 panels evaluated, the panel evaluating mature T-cell abnormalities showed the highest rate of discrepancy, whereas the panel for evaluation of myelodysplastic syndromes showed the lowest discrepancy rate. When analyzing the trends of concordance and discrepancy over time, we observed a statistically significant decrease in discrepancy rate over time, from 4% at the beginning of the 6-month period to 1.5% in the final 6-month period. The overall concordance rate was 97.7%. The remaining 2.3% of cases showed discrepancies that required a correction, underscoring the value and necessity of having a QA program. The overall discrepancy rates exhibited a gradual decline over time, indicative of the positive impact of the QA program on enhancing diagnostic competency and accuracy over time.

Expression of programmed-death ligand 1 (PD-L1) in non-small cell lung cancer (NSCLC) is typically evaluated through invasive biopsies; however, recent advances in the identification of circulating tumor cells (CTCs) may be a less invasive method to assay tumor cells for these purposes. These liquid biopsies rely on accurate identification of CTCs from the diverse populations in the blood, where some tumor cells share characteristics with normal blood cells. While many blood cells can be excluded by their high expression of CD45, neutrophils and other immature myeloid subsets have low to absent expression of CD45 and also express PD-L1. Furthermore, cytokeratin is typically used to identify CTCs, but neutrophils may stain non-specifically for intracellular antibodies, including cytokeratin, thus preventing accurate evaluation of PD-L1 expression on tumor cells. This holds even greater significance when evaluating PD-L1 in epithelial cell adhesion molecule (EpCAM) positive and EpCAM negative CTCs (as in epithelial-mesenchymal transition (EMT)). To evaluate the impact of CTC misidentification on PD-L1 evaluation, we utilized CD11b to identify myeloid cells. CTCs were isolated from patients with metastatic NSCLC using EpCAM, MUC1 or Vimentin capture antibodies and exclusion-based sample preparation (ESP) technology. Large populations of CD11b+CD45lo cells were identified in buffy coats and stained non-specifically for intracellular antibodies including cytokeratin. The amount of CD11b+ cells misidentified as CTCs varied among patients; accounting for 33-100% of traditionally identified CTCs. Cells captured with vimentin had a higher frequency of CD11b+ cells at 41%, compared to 20% and 18% with MUC1 or EpCAM, respectively. Cells misidentified as CTCs ultimately skewed PD-L1 expression to varying degrees across patient samples. Interfering myeloid populations can be differentiated from true CTCs with additional staining criteria, thus improving the specificity of CTC identification and the accuracy of biomarker evaluation.

Traditional manual gating strategies are often time-intensive, place a high burden on the analyzer, and are susceptible to bias between analyzers. Several automated gating methods have shown to exceed performance of manual gating for a limited number of cell subsets. However, many of the automated algorithms still require significant manual interventions or have yet to demonstrate their utility in large datasets. Therefore, we developed an approach that utilizes a previously published automated algorithm (OpenCyto framework) with a manually created hierarchically cell gating template implemented, along with a custom developed visualization software (FlowAnnotator) to rapidly and efficiently analyze immunophenotyping data in large population studies. This approach allows pre-defining populations that can be analyzed solely by automated analysis and incorporating manual refinement for smaller downstream populations. We validated this method with traditional manual gating strategies for 24 subsets of T cells, B cells, NK cells, monocytes and dendritic cells in 931 participants from the Health and Retirement Study (HRS). Our results show a high degree of correlation (r ≥ 0.80) for 18 (78%) of the 24 cell subsets. For the remaining subsets, the correlation was low (<0.80) primarily because of the low numbers of events recorded in these subsets. The mean difference in the absolute counts between the hybrid method and manual gating strategy of these cell subsets showed results that were very similar to the traditional manual gating method. We describe a practical method for standardization of immunophenotyping methods in large scale population studies that provides a rapid, accurate and reproducible alternative to labor intensive manual gating strategies.

AimsElimination of non-value added testing without compromising high-quality clinical care is an important mandate for laboratories in a value-based reimbursement system. The goal of this study was to determine the optimal combination of flow cytometric markers for a screening approach that balances efficiency and accuracy.MethodsAn audit over 9 months of flow cytometric testing was performed, including rereview of all dot plots from positive cases.ResultsOf the 807 cases in which leukaemia/lymphoma testing was performed, 23 were non-diagnostic and 189 represented bronchoalveolar lavage specimens. Of the remaining 595 cases, 137 (23%) were positive for an abnormal haematolymphoid population. Review of the positive cases identified minimum requirements for a screening tube as well as analysis strategies to overcome the diagnostic pitfalls noted. It is estimated that 38% fewer antibodies would be used in a screening approach, representing an opportunity for significant cost savings.ConclusionsWe provide a framework for developing an evidence-based screening combination for cost-effective characterisation of haematolymphoid malignancies, promoting adoption of ‘just-in-time’ testing systems that tailor the evaluation to the diagnostic need.

. Routine lymphocyte counting requires quality assurance validation using quality controls (QCs) that closely resemble fresh human blood leukocytes. This study aimed to evaluate a novel artificial product designed to mimic leukocyte light scatters and marker expression. . FlowCytes and TruCytes, \"artificial cell mimics\" (Slingshot Biosciences, Emeryville, CA, USA), were tested on CE-IVD-certified systems, namely FACSCanto, FACSLyric (BD Biosciences), Navios, and DxFlex (Beckman Coulter), using routine staining, lysing, fixation, and no-wash procedures for T, B, and NK counting. . FlowCytes and TruCytes provided forward and side scatter profiles comparable to human leukocytes on the FACSCanto, FACSLyric, and DxFlex systems but not on Navios despite adapting the process to be slightly different from the manufacturer's recommendations. TruCytes demonstrated robust immunolabeling of CD3, CD4, CD8, and CD19 on the FACSCanto, FACSLyric, and DxFlex systems, with fluorescence intensities and subset distributions being similar to those usually observed in fresh human blood. However, CD16 and CD56 labeling was inconsistent and depended on the antibody clones used. Regrettably, monocyte and granulocyte mimics lacked expression of CD4, CD16, and CD14. TruCytes also displayed significantly lower concentrations of TBNK lymphocyte subsets compared to healthy human blood. . FlowCytes and TruCytes show promises as internal quality controls for T cell and B cell immunophenotyping, but not NK cells. They are compatible with most CE-IVD cytometers, even when using lysis/fixation/no-wash routine diagnosis procedures. Further multicentric studies are warranted to assess their performance relative to existing products, such as stabilized human blood.