The European Myeloma Network (EMN) organized two flow cytometry workshops. The first aimed to identify specific indications for flow cytometry in patients with monoclonal gammopathies, and consensus technical approaches through a questionnaire-based review of current practice in participating laboratories. The second aimed to resolve outstanding technical issues and develop a consensus approach to analysis of plasma cells. The primary clinical applications identified were: differential diagnosis of neoplastic plasma cell disorders from reactive plasmacytosis; identifying risk of progression in patients with MGUS and detecting minimal residual disease. A range of technical recommendations were identified, including: 1) CD38, CD138 and CD45 should all be included in at least one tube for plasma cell identification and enumeration. The primary gate should be based on CD38 vs. CD138 expression; 2) after treatment, clonality assessment is only likely to be informative when combined with immunophenotype to detect abnormal cells. Flow cytometry is suitable for demonstrating a stringent complete remission; 3) for detection of abnormal plasma cells, a minimal panel should include CD19 and CD56. A preferred panel would also include CD20, CD117, CD28 and CD27; 4) discrepancies between the percentage of plasma cells detected by flow cytometry and morphology are primarily related to sample quality and it is, therefore, important to determine that marrow elements are present in follow-up samples, particularly normal plasma cells in MRD negative cases.

Chronic lymphocytic leukemia (CLL) is a disease of the elderly, characterized by immunodeficiency. Hence, patients with CLL might be considered more susceptible to severe complications from COVID-19. We undertook this retrospective international multicenter study to characterize the course of COVID-19 in patients with CLL and identify potential predictors of outcome. Of 190 patients with CLL and confirmed COVID-19 diagnosed between 28/03/2020 and 22/05/2020, 151 (79%) presented with severe COVID-19 (need of oxygen and/or intensive care admission). Severe COVID-19 was associated with more advanced age (≥65 years) (odds ratio 3.72 [95% CI 1.79-7.71]). Only 60 patients (39.7%) with severe COVID-19 were receiving or had recent (≤12 months) treatment for CLL at the time of COVID-19 versus 30/39 (76.9%) patients with mild disease. Hospitalization rate for severe COVID-19 was lower (p < 0.05) for patients on ibrutinib versus those on other regimens or off treatment. Of 151 patients with severe disease, 55 (36.4%) succumbed versus only 1/38 (2.6%) with mild disease; age and comorbidities did not impact on mortality. In CLL, (1) COVID-19 severity increases with age; (2) antileukemic treatment (particularly BTK inhibitors) appears to exert a protective effect; (3) age and comorbidities did not impact on mortality, alluding to a relevant role of CLL and immunodeficiency.

In chronic lymphocytic leukemia (CLL) the level of minimal residual disease (MRD) after therapy is an independent predictor of outcome. Given the increasing number of new agents being explored for CLL therapy, using MRD as a surrogate could greatly reduce the time necessary to assess their efficacy. In this European Research Initiative on CLL (ERIC) project we have identified and validated a flow-cytometric approach to reliably quantitate CLL cells to the level of 0.0010% (10−5). The assay comprises a core panel of six markers (i.e. CD19, CD20, CD5, CD43, CD79b and CD81) with a component specification independent of instrument and reagents, which can be locally re-validated using normal peripheral blood. This method is directly comparable to previous ERIC-designed assays and also provides a backbone for investigation of new markers. A parallel analysis of high-throughput sequencing using the ClonoSEQ assay showed good concordance with flow cytometry results at the 0.010% (10−4) level, the MRD threshold defined in the 2008 International Workshop on CLL guidelines, but it also provides good linearity to a detection limit of 1 in a million (10−6). The combination of both technologies would permit a highly sensitive approach to MRD detection while providing a reproducible and broadly accessible method to quantify residual disease and optimize treatment in CLL.

BACKGROUND: The WHO and iwCLL diagnostic criteria for CLL rely on morphology and immunophenotype based on the co-expression of CD19/CD5/CD23 on B-cells with weak CD20 and monoclonal sIg expression. These diagnostic criteria are likely to persist in the near future because there is no specific diagnostic molecular abnormality for CLL. The current criteria have some limitations affecting reproducibility, particularly flexibility in marker expression with many centres using a scoring system that permits absence of CD5 or CD23. Potentially informative new markers have been identified but there is no consensus yet on which should be routinely assessed. AIM: To identify reproducible criteria and to achieve a consensus on markers recommended for the diagnosis of CLL METHODS: ERIC/ESCCA members were invited to classify 35 flow-cytometry markers as being required or recommended for the diagnosis of CLL. Consensus was considered to be achieved if >75% of participants agreed on the marker classification. A diagnostic panel was identified by the steering committee and characteristics of component markers that could be reproducibly validated within an individual laboratory were identified. The proposed panel was assessed in 13 different centres. RESULTS: Responses were received from 154 members (100 laboratory staff, 14 clinicians and 36 from both laboratory and clinic) with a diagnostic workload >20 cases per week in 23/154 (15%), 5-20 in 82/154 (53%) and <5 cases per week in 49/154 (32%). The consensus minimum diagnostic panel should include : CD19, CD5, CD20, CD23, Kappa and Lambda. Participants recommended the following markers: CD38, CD45, CD79b, CD10, CD22, CD43, CD200, and FMC7. A minimum and recommended panel with reproducible criteria for component reagents were determined and the criteria were applied to 10,876 cases diagnosed with a B-LPD, of which 8120 were CD5+ B-LPD. Out of 5947 sent as a primary referrals for diagnosis, 4493 (75.6%) met the proposed diagnostic criteria for CLL, 821 (13.8%) did not and had a clear alternative diagnosis (e.g. MCL) and 633 (10.6%) would not be readily classified by flow cytometry if the proposed criteria were applied. Out of 2173 cases previously diagnosed as CLL at another centre, 2028 (93.3%) met the proposed diagnostic criteria, 19 (0.9%) had a clear alternative diagnosis while 126 (5.8%) did not meet the flow-cytometry criteria. CONCLUSIONS: We present flow-cytometry criteria for the diagnosis of CLL largely consistent with current practice. In addition, reproducible definitions of the required expression pattern and performance characteristics of reagents are provided. Prospective evaluation of the proposed criteria as well as a parallel project to facilitate definitive diagnosis of CD5+ B-LPD cases that do not meet the proposed criteria are underway. Figure 1. required and recommended markers for use in the diagnosis of CLL with reagent specification based on expression patterns in normal peripheral blood. Figure 1. required and recommended markers for use in the diagnosis of CLL with reagent specification based on expression patterns in normal peripheral blood. ‡ Weak expression = median fluorescence intensity at least 20% lower than median for normal peripheral blood B-cells, reference range determined within each laboratory, based on ICSH/ISLH/CLIA guidelines for reproducibility *consensus, not specifically validated Disclosures Rawstron: Abbvie: Honoraria; Pharmacyclics: Research Funding; Celgene: Honoraria; Roche: Honoraria; BD Biosciences: Patents & Royalties; Gilead: Honoraria, Research Funding. Cuneo:Roche: Speakers Bureau; Gilead: Speakers Bureau; Jannsen: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Trneny:Celgene: Consultancy, Honoraria, Other: Travel, accommodations, expenses, Research Funding. Mulligan:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi Aventis: Research Funding. Hillmen:Celgene: Research Funding; Gilead: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; GSK: Consultancy, Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding. Hallek:Gilead: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Boehringher Ingelheim: Honoraria, Other: Speakers Bureau and/or Advisory Boards; Janssen: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Mundipharma: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Celgene: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Roche: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; AbbVie: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Pharmacyclics: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding. Ghia:AbbVie: Consultancy; Janssen: Consultancy; Roche: Consultancy, Research Funding; Adaptive: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau; GSK: Research Funding; Acerta Pharma BV: Research Funding; Pharmacyclics: Consultancy.