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Cellular interferon-gamma based assay for diagnosis of pulmonary tuberculosis
Maha M Fathy1, Ayman Asaad, Mona Mansour
1Microbiology & Immunology Department, Faculty of Medicine, Ain Shams University, Egypt.
Insights
An interferon gamma (IFN-γ) release assay shows promise for diagnosing active pulmonary tuberculosis. This in vitro test detects T-cell responses to Mycobacterium tuberculosis antigens, offering a potential new diagnostic tool.
Area of Science:
- Immunology
- Infectious Diseases
- Diagnostics
Background:
- Interferon gamma (IFN-γ) release assays measure T-cell responses to Mycobacterium tuberculosis (MTB) antigens like ESAT-6 and CFP-10.
- These assays represent a significant advancement in diagnosing tuberculosis.
Purpose of the Study:
- To evaluate the diagnostic potential of an in vitro IFN-γ production assay for pulmonary tuberculosis (TB).
Main Methods:
- The study analyzed peripheral blood mononuclear cells from 40 patients in Egypt.
- An enzyme-linked immunospot technique was used to detect IFN-γ secretion in response to MTB antigens (ESAT-6, CFP-10).
- Patients were categorized into suspected TB (bacteriologically confirmed and unconfirmed) and control groups.
Main Results:
- The IFN-γ assay demonstrated a sensitivity of 91.7% for bacteriologically confirmed TB cases.
- For suspected TB cases not bacteriologically confirmed, the assay was positive in 66.7%.
- The assay showed a specificity of 75% and was negative in all non-tuberculous control patients.
Conclusions:
- The in vitro IFN-γ release assay shows significant potential as a valuable diagnostic tool for active pulmonary tuberculosis.
- The assay's ability to detect T-cell responses to specific MTB antigens supports its utility in TB diagnosis.
Abstract:
A major breakthrough in recent years has been the development of an in vitro assays that measure T-cell release of interferon gamma (IFN-gamma) in response to stimulation with antigens specific to Mycobacterium tuberculosis (MTB) such as early secreted antigenic target 6 (ESAT6) and culture filtrate protein 10 (CFP10). This study aimed at evaluating the diagnostic potential of IFN-gamma in vitro production assay for diagnosis of pulmonary tuberculosis. The study included 40 patients from Abbasia Chest Hospital, Cairo, Egypt. Thirty patients had the provisional clinical and radiological diagnosis of pulmonary tuberculosis (TB), twenty of them had positive acid fast (AF) sputum smears (group I), and ten had negative smears (group II). Bacteriological confirmation of TB was based on cultivation on L.J solid media (group I & II), and by BACTEC radiometric assay (group II). Ten patients with non tuberculous chest diseases were also included as a control group (group III). Effector T cells, within the peripheral blood mononuclear cells, which secrete IFN-gamma in response to stimulation by antigens specific for MTB (ESAT-6 and CFP-10) were analyzed in all subjects using a commercially available assay based on the enzyme linked immunospot technique. We demonstrated that 24 out of 30 (80%) suspected tuberculous patients were bacteriologically confirmed based on positive AF smears and/or culture. In vitro IFN-gamma release assay was positive in 22 of them giving a sensitivity of 91.7%. In the remaining 6 who were not confirmed bacteriologically, the assay showed positive results in 4 (66.7%) of them. Based on bacteriological diagnosis as the gold standard for diagnosis of pulmonary TB, the specificity of the assay was found to be 75%. However the assay results were negative in all non tuberculous patients (group III). It is concluded that the used in vitro IFN-gamma release assay has the potential to become a useful diagnostic tool for active tuberculosis.
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