UNASSIGNED: Paroxysmal nocturnal haemoglobinuria (PNH) is a rare haematologic disease characterised by intravascular haemolysis, thrombophilia and bone marrow failure. There is a lack of established clinical guidance on the screening, diagnosis and manage-ment of PNH in Singapore. A relatively low level of awareness among healthcare professionals regarding PNH manifestations further contributes to diagnostic delays. Additionally, limited access to complement inhibitors, like eculizumab, may delay treatment and impact patient outcomes.
UNASSIGNED: Nine haematologists from different institu-tions in Singapore convened to formulate evidence-based consensus recommendations for optimising the diagnosis and management of patients with PNH and improving access to novel treatments. The experts reviewed the existing literature and international guidelines published from January 2010 to July 2023, focusing on 7 clinical questions spanning PNH screening, diagnostic criteria, investigations, treatment and monitoring of subclinical and classic disease, PNH with underlying bone marrow disorders, and PNH in pregnancy. A total of 181 papers were reviewed to formulate the statements. All experts voted on the statements via 2 rounds of Delphi and convened for an expert panel discussion to finetune the recommendations.
UNASSIGNED: Sixteen statements have been formulated for optimising the screening, diagnosis and management of PNH. Upon confirmation of PNH diagnosis, individuals with active haemolysis and/or thrombosis should be considered for anti-complement therapy, with eculizumab being the only approved drug in Singapore.
UNASSIGNED: The current recommendations aim to guide the clinicians in optimising the screening, diagnosis and management of PNH in Singapore.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal disease with abnormal hematopoietic stem cells that causes intravascular hemolytic anemia, thrombosis, and peripheral blood cytopenia. It has a chronic progressive course and can be fatal in severe cases if not treated aggressively. Complement inhibitors are the first-line recommended treatment for hemolysis-related symptoms of PNH. With the rapid development of new complement inhibitors, it is critical to quickly screen and confirm the diagnosis, identify patients with complement inhibitor indications, and monitor breakthrough hemolysis and extravascular hemolysis during complement inhibitor therapy. Drawing on the most recent guidelines, works of literature, and meta-reviews from around the world, as well as combining with experience from the experts, this consensus focused on PNH screening principles, the significance of PNH cloning detection, and post-treatment monitoring of terminal complement inhibitors, which may contribute to a better understanding of diagnosis and treatment monitoring in the era of complement inhibitors.
阵发性睡眠性血红蛋白尿症（paroxysmal nocturnal hemoglobinuria，PNH）是一种罕见的造血干细胞异常克隆性疾病，以血管内溶血性贫血、血栓形成和外周血细胞减少为主要表现，呈慢性进展性病程，严重者可危及生命。补体抑制剂是治疗PNH溶血相关症状的一线推荐药物。随着补体抑制剂领域的快速发展，加强对PNH的筛查、快速诊断，判断需要用补体抑制剂治疗的患者，在补体抑制剂治疗过程中监测突破性溶血、血管外溶血等，对患者的生存、生活质量改善有着重要意义。为促进PNH临床诊疗的规范，本共识参考国内外最新指南和文献，荟萃国内外最新研究成果，并结合专家团队经验，聚焦PNH筛查原则、PNH克隆检测意义、末端C5补体抑制剂治疗后监测等问题，旨在为PNH的筛查、诊断和补体抑制剂时代的治疗监测提供参考意见。.

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BACKGROUND: Flow cytometry-based paroxysmal nocturnal hemoglobinuria (PNH) testing involves utilization of monoclonal antibodies against GPI-linked proteins and FLAER. The ability of FLAER to bind to a wide variety of GPI-linked structures and to be utilized across different leukocyte subsets is remarkable. We hypothesize that FLAER as a standalone reagent may be equally effective for detecting PNH clones. The present study intends to compare the results of a FLAER alone-based strategy to the recommended FLAER+GPI-linked protein-based approach for applicability in clinical settings.
METHODS: EDTA-anticoagulated blood samples from patients for PNH workup were tested for PNH by multiparametric flow cytometry. A conventional panel comprising gating markers (CD45 for WBC, CD15 for granulocytes, and CD64 for monocytes) and a combination of FLAER and GPI-linked markers, such as CD24 and CD14, henceforth referred to as the \"routine panel,\" was employed. Second, a \"FLAER-only panel\" comprising the gating markers and FLAER alone (excluding the GPI-linked markers CD24 and CD14) was set up. The samples were processed using the lyse-wash-stain-wash technique, and events were acquired on BC Navios Ex flow cytometer (Beckman Coulter, Inc., USA) and analyzed on Kaluza Software 2.1. The presence of a PNH clone was reported at a value of ≥0.01%.
RESULTS: A total of 209 patients were tested. Both panels found a PNH clone in 20.1% of patients (n = 42/209) with a 100% concordance rate. The PNH clone range for granulocytes was 0.01%-89.68%, and for monocyte was 0.04%-96.09% in the routine panel. The range in the FLAER-only panel for granulocytes was 0.01%-89.61%, and for monocytes, it was 0.01%-96.05%. Pearson correlation statistics revealed a significant correlation between the size of the PNH clone of granulocytes and monocytes among the two panels tested (granulocytes r = 0.9999, p < 0.0001, 95% CI = 0.9999 to 1.000; monocytes r = 0.9974, p < 0.0001, 95% CI = 0.9966-0.9980).
CONCLUSIONS: Based on our results, FLAER as a standalone marker is specific and sensitive for identifying PNH clones in granulocytes and monocytes, even for high-sensitivity PNH assay. The proposed \"FLAER-only panel\" panel is efficient and cost-effective for highly sensitive PNH testing in two different cell lineages, especially in resource-limited clinical settings.

We examined the frequencies and sizes of glycosylphosphatidylinositol (GPI)-deficient cells as per the International Clinical Cytometry Society/European Society for Clinical Cell Analysis (ICCS/ESCCA) consensus guidelines for the high-sensitivity detection of GPI-deficient cells.
In 2018, the ICCS/ESCCA guidelines for the high-sensitivity detection of GPI-deficient cells were published. We evaluated frequencies and sizes of GPI-deficient red blood cells (RBCs), neutrophils, and monocytes as determined using the ICCS/ESCCA guidelines and Clinical and Laboratory Standards Institute (CLSI) guidelines in patients with a hematologic malignancy, aplastic anemia, or cytopenia.
A total of 106 (38.7%) patients exhibited GPI deficiency in at least one blood cell lineage. GPI-deficient cells of one or more lineages were found in 62.7% of patients with a hematologic malignancy, 51.1% of patients with aplastic anemia, and 23.4% of patients with cytopenia. GPI-deficient monocytes were most frequently detected in all three groups. By population size, GPI-deficient clones (>1%) in monocytes were mostly detected in patients with a hematologic malignancy or aplastic anemia. Rare cells with GPI deficiency (<0.1%) in monocytes were most common among patients with cytopenia.
High-sensitive flow cytometry analysis including monocytes may be necessary for patients with a hematologic disorder.

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Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematopoietic stem cell disorder resulting from the somatic mutation of the X-linked phosphatidyl-inositol glycan complementation Class A (PIG-A) gene. Depending on the severity of the mutation in the PIG-A gene, there is a partial or absolute inability to make glycosylphosphatidyl-inositol (GPI)-anchored proteins including complement-defense structures such as CD55 and CD59 on RBCs and WBCs. Flow cytometric detection of PNH clones has become the gold standard and has played an increasingly important role in the diagnosis, monitoring, and clinical management of patients with PNH. Recently, a 4-part set of Consensus Guidelines have been published by flow experts in the field to address the key assay-specific considerations for the identification of PNH clones in RBC and WBC, how to report such data and a full validation document for the assays described. Below, we have summarized the most significant aspects of this International effort.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by intravascular hemolysis, thrombophilia, and marrow failure. Its phenotype is due to absent or reduced expression of GPI-linked complement regulators and subsequent sensitivity of hematopoietic cells to complement-mediated damage and lysis. Introduction of the terminal complement inhibitor eculizumab drastically improved outcomes in PNH patients; however, despite this improvement, there remain several challenges faced by PNH patients and physicians who care for them. One of the most important is increasing awareness of the heterogeneity with which patients can present, which can lead to significant delays in recognition. Data from the Canadian PNH Registry are presented to demonstrate the variety of presenting symptoms. In Canada, geography precludes consolidation of care to just a few centers, so management is distributed across academic hospitals, linked together as the Canadian PNH Network. The Network over the last several years has developed educational programs and clinical checklists and has worked to standardize access to diagnostics across the country. Herein, we address some of the common diagnostic and therapeutic challenges faced by PNH physicians and give our recommendations. Gaps in knowledge are also addressed, and where appropriate, consensus opinion is provided.

OBJECTIVE: Paroxysmal nocturnal hemoglobinuria (PNH) is a severe, life-threatening disorder for which early diagnosis is essential. However, given the rarity of the disease and non-specificity of symptoms, correct diagnosis may be delayed or missed. While various hematologic guidelines note common signs and symptoms associated with PNH, international expert consensus based on real-world clinical experience and an actionable algorithm for non-specialists to facilitate screening and diagnosis are lacking. The objective of the study is to develop a clinically relevant, consensus-driven screening and diagnostic algorithm on PNH for non-specialist clinicians.
METHODS: An expert advisory committee of PNH experts from North America, Europe, and Japan was convened, and a modified Delphi methodology was employed to develop an algorithm to assist non-specialist clinicians in identifying signs/symptoms of PNH and conducting appropriate differential diagnosis. Twelve globally representative Delphi panelists with clinical expertise in PNH were identified and recruited. Panelists provided their differential diagnosis for 5 blinded case studies via 2 rounds of online questionnaires. Responses mentioned by >50% of panelists in the first round were included in the second-round questionnaire, at which point consensus was attained if >80% of panelists agreed on an approach.
RESULTS: Consensus was reached for 95% of screening and diagnostic decision points and 90% of tests required at decision points.
CONCLUSIONS: These results facilitated development of a consensus-based, clinically relevant algorithm, providing non-specialist clinicians with actionable guidance on PNH screening and diagnosis.

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