Laboratory Accuracy Improvement in the UK NEQAS Leucocyte Immunophenotyping Immune Monitoring Program: An Eleven-Year Review via Longitudinal Mixed Effects Modeling

European flow cytometry quality assurance guidelines for the diagnosis of primary immune deficiencies and assessment of immune reconstitution following B cell depletion therapies and transplantation

Over the last 15 years activity of diagnostic flow cytometry services have evolved from monitoring of CD4 T cell subsets in HIV-1 infection to screening for primary and secondary immune deficiencies syndromes and assessment of immune constitution following B cell depleting therapy and transplantation. Changes in laboratory activity in high income countries have been driven by initiation of anti-retroviral therapy (ART) in HIV-1 regardless of CD4 T cell counts, increasing recognition of primary immune deficiency syndromes and the wider application of B cell depleting therapy and transplantation in clinical practice. Laboratories should use their experience in standardization and quality assurance of CD4 T cell counting in HIV-1 infection to provide immune monitoring services to patients with primary and secondary immune deficiencies. Assessment of immune reconstitution post B cell depleting agents and transplantation can also draw on the expertise acquired by flow cytometry laboratories for detection of CD34 stem cell and assessment of MRD in hematological malignancies. This guideline provides recommendations for clinical laboratories on providing flow cytometry services in screening for immune deficiencies and its emerging role immune reconstitution after B cell targeting therapies and transplantation.

Inter-laboratory method validation of CD34+ flow-cytometry assay: the experience of Turin Metropolitan Transplant Centre

The Turin Metropolitan Transplant Centre (CIC 305) includes four flow-cytometry laboratories assessing quality control on hematopoietic stem cells (HSC) with different instruments and operators. Therefore, the CD34+ enumeration assay should be validated on a regular basis. We describe here the validation plan to test the inter-laboratory reproducibility of CD34+ enumeration assay, based on the risk analysis. Stabilized blood samples were analysed using Stem-Kit reagent according to manufacturer's instructions and acquired using the Beckman Coulter Navios at Regina Margherita Children's' Hospital (305-1), Beckman Coulter FC500 at Candiolo Cancer Institute FPO-IRCCS (305-2), BD Biosciences FACSLyric™ at S. Luigi Hospital (305-3), and Beckman Coulter Navios EX at Mauriziano Hospital (305-4). The ISHAGE guidelines were followed for estimating % and absolute number of CD34+ cells in single-platform method. For each sample repeatability limit (r), reproducibility error, uncertainty of reproducibility error and coefficient of variation (CV) were reported. The repeated measurements from each laboratory or instrument have a variability, expressed as reproducibility error, lower than the repeatability limit for that single parameter. The corrected reproducibility error is always lower than the repeatability limit except for the percentage value of the "low" count. The analysis of inter-laboratory variance is within the maximum acceptable variance value, and the CV of all measurements for each parameter is less than 8%, indicating low measurement variability among laboratories. Evaluating the overall data, we can conclude that the four laboratories are perfectly aligned and the results are reproducible.

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.

External quality assessment of flow cytometric bronchoalveolar lavage cellular analysis: 20 years' experience in The Netherlands

BACKGROUND

Bronchoalveolar (BAL) cellular analysis can be supportive in the diagnosis of interstitial lung disease. The flow cytometric analysis of BAL fluid cells is complicated by cell fragility and adherence and autofluorescence of macrophages, making conventional analysis of BAL fluid cells as done in external quality schemes (EQA) for blood lymphocyte subsets, not representative. Following a procedure for stabilized BAL cells, a separate EQA was set up. The results of 20 years' experience are presented.

METHODS

From each round between 2000 and 2020 the following flow cytometric parameters were recorded from each participant: total lymphocyte population (TLY), CD3+ lymphocytes, CD3+ CD4+ lymphocytes, CD3+ CD8+ lymphocytes, CD3- CD16+/56+ lymphocytes, CD19+ lymphocytes and CD103 + CD3+ lymphocytes. In addition, the eosinophils and neutrophils were recorded. The mean and standard deviation of each parameter per round were calculated. The 40 rounds were divided in four respective groups of 10 in order to compare the results as function of time. In addition the interpretation of the results of participants was scored.

RESULTS

The median SD in the four groups was below 10% for all parameters except for TLY and the CD103+ CD3+ lymphocytes. No improvement in time was observed for any (sub)population except for the CD3+ CD4+ subset. Interpretation of the results varied based on disease, with greatest consensus for sarcoidosis cases and lowest for nonspecific interstitial lung disease cases.

CONCLUSIONS

A dedicated EQA for BAL fluid cellular analysis appears to be justified as the test material is substantially different from that of peripheral blood. We show that adequate analytical and post-analytical quality control can be achieved.

Role of flow cytometry in evaluation of the cellular therapy products used in haematopoietic stem cell transplantation

Cellular therapy nowadays includes various products from haematopoietic stem cells (HSC) collected from bone marrow, peripheral blood, and umbilical cord blood to more complex adoptive immune therapy for the treatment of malignant diseases, and gene therapy for inherited immune deficiencies. Broader utilization of cellular therapy requires extensive quality testing of these products that should fulfil the same requirements regarding composition, purity, and potency nevertheless they are manufactured in various centres. Technical improvements of the flow cytometers accompanied by the increased number of available reagents and fluorochromes used to conjugate monoclonal antibodies, enable detailed and precise insight into the function of the immune system and other areas of cell biology, and allows cell evaluation based on size, shape, and morphology or assessment of cell surface markers, as well as cell purity and viability, which greatly contributes to the development and progress of the cell therapy. The aim of this paper is to give an overview of the current use and challenges of flow cytometry analysis in quality assessment of cellular therapy products, with regard to basic principles of determining HSC and leukocyte subpopulation, assessment of cells viability and quality of thawed cryopreserved HSC as well as the importance of validation and quality control of flow cytometry methods according to good laboratory practice.

An Extensive Quality Control and Quality Assurance (QC/QA) Program Significantly Improves Inter-Laboratory Concordance Rates of Flow-Cytometric Minimal Residual Disease Assessment in Acute Lymphoblastic Leukemia: An I-BFM-FLOW-Network Report

Simple Summary

Standardization of flow-cytometric assessment of minimal residual disease in acute lymphoid leukemia (ALL) is necessary to allow concordant multicentric application of the methodology. This is a prerequisite for internationally collaborative trials, such as the AIEOP-BFM-ALL and the ALL IC-BFM trial. We developed and applied a comprehensive training and quality control program involving a large number of international laboratories within the I-BFM consortium to complement standardization of the methodology with an educational component as well as with persistent quality control measures to allow large ALL treatment trials which use multi-laboratory FCM-MRD assessments for risk stratification of pediatric patients with ALL.

Abstract

Monitoring of minimal residual disease (MRD) by flow cytometry (FCM) is a powerful prognostic tool for predicting outcomes in acute lymphoblastic leukemia (ALL). To apply FCM-MRD in large, collaborative trials, dedicated laboratory staff must be educated to concordantly high levels of expertise and their performance quality should be continuously monitored. We sought to install a unique and comprehensive training and quality control (QC) program involving a large number of reference laboratories within the international Berlin-Frankfurt-Münster (I-BFM) consortium, in order to complement the standardization of the methodology with an educational component and persistent quality control measures. Our QC and quality assurance (QA) program is based on four major cornerstones: (i) a twinning maturation program, (ii) obligatory participation in external QA programs (spiked sample send around, United Kingdom National External Quality Assessment Service (UK NEQAS)), (iii) regular participation in list-mode-data (LMD) file ring trials (FCM data file send arounds), and (iv) surveys of independent data derived from trial results. We demonstrate that the training of laboratories using experienced twinning partners, along with continuous educational feedback significantly improves the performance of laboratories in detecting and quantifying MRD in pediatric ALL patients. Overall, our extensive education and quality control program improved inter-laboratory concordance rates of FCM-MRD assessments and ultimately led to a very high conformity of risk estimates in independent patient cohorts.

Validation of a flow cytometry-based method to quantify viable lymphocyte subtypes in fresh and cryopreserved hematopoietic cellular products

BACKGROUND AIMS

Adoptive cellular therapy with immune effector cells (IECs) has shown promising efficacy against some neoplastic diseases as well as potential in immune regulation. Both inherent variability in starting material and variations in cell composition produced by the manufacturing process must be thoroughly evaluated with a validated method established to quantify viable lymphocyte subtypes. Currently, commercialized immunophenotyping methods determine cell viability with significant errors in thawed products since they do not include any viability staining. We hereby report on the validation of a flow cytometry-based method for quantifying viable lymphocyte immunophenotypes in fresh and cryopreserved hematopoietic cellular products.

METHODS

Using fresh or frozen cellular products and stabilized blood, we report on the validation parameters accuracy, uncertainty, precision, sensitivity, robustness and contamination between samples for quantification of viable CD3+, CD4+ T cells, CD8+ T cells, CD3-CD56+CD16+/- NK cells, CD19+ B cells and CD14+ monocytes of relevance to fresh and cryopreserved hematopoietic cellular products using the Cytomics FC500 cytometer (Beckman Coulter).

RESULTS

The acceptance criteria set in the validation plan were all met. The method is able to accommodate the variability in absolute numbers of cells in starting materials collected or cryopreserved from patients or healthy donors (uncertainty of ≤20% at three different concentrations), stability over time (compliance over 3 years during regular inter-laboratory comparisons) and confidence in meaningful changes during cell processing and manufacturing (intra-assay and intermediate precision of 10% coefficient of variation). Furthermore, the method can accurately report on the efficacy of cell depletion since the lower limit of quantification was established (CD3+, CD4+ and CD8+ cells at 9, 8 and 8 cells/µL, respectively). The method complies with Foundation for the Accreditation of Cellular Therapy (FACT) standards for IEC, FACT-Joint Accreditation Committee of ISCT-EBMT (JACIE) hematopoietic cell therapy standards, International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use Q2(R1) and International Organization for Standardization 15189 standards. Furthermore, it complies with Ligand Binding Assay Bioanalytical Focus Group/American Association of Pharmaceutical Scientists, International Council for Standardization of Hematology/International Clinical Cytometry Society and European Bioanalysis Forum recommendations for validating such methods.

CONCLUSIONS

The implications of this effort include standardization of viable cell immunophenotyping of starting material for cell manufacturing, cell selection and in-process quality controls or dosing of IECs. This method also complies with all relevant standards, particularly FACT-JACIE standards, in terms of enumerating and reporting on the viability of the "clinically relevant cell populations."

Harmonization of External Quality Assessment Schemes and their role - clinical chemistry and beyond

The article tries to reply to the following three questions: Are External Quality Assessment Schemes (EQAS) really fit for purpose? Are all schemes equivalent and sufficiently harmonized? Is the role of EQAS similar and necessary in all branches of laboratory medicine? Although the reply to the first two questions is, unfortunately, negative for several reasons (lack of commutable material with reference method values, EQAS with different scopes, etc.), the reply to the third one is positive: EQAS are a necessary source of information on trueness and accuracy and must be fully developed for all the branches of the clinical laboratory.

Peripheral blood immunophenotyping in a large cohort of patients with Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is one of the more common inherited bone marrow failure syndromes, characterized by neutropenia, occasional thrombocytopenia, and anemia. Bone marrow evaluation reveals an increased number of monocytes and mature B cells along with decreased granulocytes. However, little is known about the subpopulations of peripheral blood cells, and few previous publications have been based on a small number of patients. Here, we report a comprehensive immunophenotypic analysis from a cohort of 37 SDS patients who display impairment mostly in the myeloid compartment with a deficiency also in the number of B cells and CD4/CD8 double-negative T cells.