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Flow cytometry-based diagnostic approach for inborn errors of immunity: experience from Algeria
Azzeddine Tahiat1, Reda Belbouab2, Abdelghani Yagoubi3
1Department of Medical Biology, Rouiba Hospital, University of Algiers 1, Algiers, Algeria.
Insights
Flow cytometry (FCM) is a valuable tool for diagnosing inborn errors of immunity (IEIs), especially in resource-limited settings. Our study shows FCM aids in diagnosing and categorizing diverse IEIs, offering crucial insights for patient management.
Area of Science:
- Clinical Immunology
- Diagnostic Pathology
- Medical Laboratory Science
Background:
- Inborn errors of immunity (IEIs) are a heterogeneous group of genetic disorders affecting the immune system.
- Accurate and timely diagnosis is crucial for effective management and improving patient outcomes.
- Flow cytometry (FCM) offers a powerful platform for evaluating immune cell populations and functions.
Purpose of the Study:
- To retrospectively review the utility of flow cytometry (FCM) in diagnosing inborn errors of immunity (IEIs).
- To present practical, FCM-based diagnostic approaches tailored to various clinical scenarios.
- To share experience from a single center in Algeria, highlighting its applicability in diverse settings.
Main Methods:
- Retrospective review of pediatric and adult patients with suspected immunodeficiency.
- Application of FCM for lymphocyte subset analysis, protein expression, and functional assays.
- Analysis of diagnostic yield for 70 different IEIs across 9 categories.
Main Results:
- FCM was utilized in the diagnosis of 670 patients over a nearly seven-year period.
- A total of 514 patients (76.7%) received diagnoses or supportive evidence for IEIs via FCM.
- FCM provided direct diagnoses for conditions like SCID and MHC class II deficiency, and suggestive evidence for others, guiding genetic testing.
Conclusions:
- Flow cytometry is a highly valuable and cost-effective method for diagnosing most IEIs.
- FCM is particularly relevant in low-income countries with limited access to genetic testing.
- FCM analysis provides direct diagnostic insights, suggests underlying genetic defects, and aids in gene prioritization for IEIs.
Purpose:
In 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.
Methods:
Between 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.
Results:
Over 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.
Conclusion:
Flow 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.
