Use of rapid test for IFN-gamma detection for the diagnosis of primary immunodeficiency diseases affecting cellular immunity IntroductionPrimary immunodeficiencies are complex disorders that can affect several components of the immune system. They are considered rare diseases, but they present relevant statistics when analyzed together - about 1 for every 2000 live births.The patients affected are susceptible to infections (often recurrent) and adverse reactions to vaccines, which contribute to the increase in mortality and morbidity of this population at an early age. When the defect is related to the cellular component of the immune response, there may be impairment of cell proliferation, coestimulation and signaling, cytokine production - crucial events for an adequate immune response.With advances in technology and healthcare professionals' engagement, there has been a significant increase in the number of patients diagnosed and registered with primary immunodeficiencies. However, it is known that these disorders are still underdiagnosed. Poor access to healthcare services is responsible for part of this situation. The lack of specific and accurate laboratory diagnostic methods also contributes to the underdiagnosis - nowadays, only large specialized centers are capable of detecting the majority of cases.One of the widely used methods for testing the cellular immune response is the evaluation of cell proliferation and cytokine production through flow cytometry. Although it provides important information about the patient's immune response, flow cytometry is an expensive and complex method that demands at least two days for results to be released and it is not universally standardized.Recently, a rapid test (QIAGEN's QuantiferonMonitor) followed by an enzyme-linked immunosorbent assay (ELISA) has been used to quantify the IFN-gamma production after in vitro non-specific stimulation, allowing an evaluation of the innate and cellular immune responses within one day.AimThe aim of this study is to compare the two laboratory tests in their ability of detecting impairment of the cellular immune response, evaluating then their sensitivity for the diagnosis of primary T cell immunodeficiencies.Patients and MethodsAfter approval by the Research Ethics Committee and signature of consent/ assentment terms, we will recruit patients from the Clinical Immunology Division of Universidade Federal de São Paulo (UNIFESP). The participants will be divided into two groups according to previous diagnoses: patients with immunodeficiency disorders with cellular impairment (n = 15) and patients with immunodeficiency disorders without cellular impairment (n = 15). Healthy individuals will also be included to form the control group (n = 15). Patients' data will be collected from their medical record in order to characterize the primary immunodeficiency. From the individuals in the control group, information about general aspects of health, age and sex will be obtained. Next, a 5 mL blood sample will be collected for cell lymphoproliferation assay following in vitro stimulation with phytohemagglutinin, with measurement of CD25 expression on lymphocyte surface and intracellular IFN-gamma by flow cytometry; the same sample will be analyzed using the QuantiferonMonitor kit (QIAGEN), according to the manufacturer's instructions.Analysis of resultsThe results will be analyzed in order to compare the two laboratory tests and their ability to diagnose cell type immunodeficiencies by assessing the sensitivity and specificity of the QuantiferonMonitor, considering the lymphoproliferation assay as gold standard.This is expected to fasten the diagnosis and facilitate the clinical management of patients suspected of having primary immunodeficiency of the cell type, in order to allow the early initiation of follow-up and treatment, contributing to the increase in quality and expectancy of life of this population.
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