Table_2_Flow cytometry-based diagnostic approach for inborn errors of immunity: experience from Algeria.docx

PurposeIn this study, we retrospectively reviewed the use of flow cytometry (FCM) in the diagnosis of inborn errors of immunity (IEIs) at a single center in Algeria. Sharing insights into our practical experience, we present FCM based diagnostic approaches adapted to different clinical scenarios.
MethodsBetween May 2017 and February 2024, pediatric and adult patients presenting with clinical features suggestive of immunodeficiency were subjected to FCM evaluation, including lymphocyte subset analysis, detection of specific surface or intracellular proteins, and functional analysis of immune cells.
ResultsOver a nearly seven-year period, our laboratory diagnosed a total of 670 patients (372 (55.5%) males and 298 (44.5%) females), distributed into 70 different IEIs belonging to 9 different categories of the International Union of Immunological Societies classification. FCM was used to diagnose and categorize IEI in 514 patients (76.7%). It provided direct diagnostic insights for IEIs such as severe combined immunodeficiency, Omenn syndrome, MHC class II deficiency, familial hemophagocytic lymphohistiocytosis, and CD55 deficiency. For certain IEIs, including hyper-IgE syndrome, STAT1-gain of function, autoimmune lymphoproliferative syndrome, and activated PI3K delta syndrome, FCM offered suggestive evidence, necessitating subsequent genetic testing for confirmation. Protein expression and functional assays played a crucial role in establishing definitive diagnoses for various disorders. To setup such diagnostic assays at high and reproducible quality, high level of expertise is required; in house reference values need to be determined and the parallel testing of healthy controls is highly recommended.
ConclusionFlow cytometry has emerged as a highly valuable and cost-effective tool for diagnosing and studying most IEIs, particularly in low-income countries where access to genetic testing can be limited. FCM analysis could provide direct diagnostic insights for most common IEIs, offer clues to the underlying genetic defects, and/or aid in narrowing the list of putative genes to be analyzed.

【研究目的】本研究回顾性分析了阿尔及利亚单中心内流式细胞术（flow cytometry, FCM）在原发性免疫缺陷病（inborn errors of immunity, IEIs）诊断中的应用。结合本中心的实践经验，本文提出适配不同临床场景的基于FCM的诊断方案。

【研究方法】2017年5月至2024年2月期间，本中心对表现出疑似免疫缺陷临床特征的儿科及成人患者开展流式细胞术检测，检测内容包括淋巴细胞亚群分析、特定表面或细胞内蛋白检测，以及免疫细胞功能分析。

【研究结果】近7年的研究周期内，本实验室共确诊670例患者（男性372例，占比55.5%；女性298例，占比44.5%），所患疾病涵盖国际免疫学会联合会（International Union of Immunological Societies）分类体系下9大类共70种原发性免疫缺陷病。其中514例（76.7%）患者的IEI诊断及分类通过流式细胞术完成。流式细胞术可直接为重症联合免疫缺陷、Omenn综合征、MHC II类缺陷、家族性噬血细胞性淋巴组织细胞增生症以及CD55缺陷等疾病提供明确的诊断依据。针对高IgE综合征、STAT1功能获得性突变、自身免疫性淋巴细胞增生综合征以及活化PI3Kδ综合征等部分原发性免疫缺陷病，流式细胞术仅能提供疑似佐证，需后续开展基因检测以明确诊断。蛋白表达与功能实验在多种疾病的确诊过程中发挥关键作用。若要建立高质量且可重复的此类诊断实验体系，需具备高水平专业技术经验，应确定实验室内部参考值，并强烈推荐同步开展健康对照检测。

【研究结论】流式细胞术已成为诊断与研究多数原发性免疫缺陷病的高价值且成本效益比优异的工具，尤其适用于基因检测资源有限的低收入国家。流式细胞术分析可为多数常见原发性免疫缺陷病提供直接诊断依据，为潜在遗传缺陷提供线索，并/或有助于缩小待分析候选基因的范围。