Улога на Quantiferon TB Gold тестот во дијагнозата на активна туберкулоза и латентна туберкулозна инфекција во детската возраст

Abstract

Introduction: Tuberculosis (TBC) according to the World Health Organization is defined as the infectious bacterial disease caused by Mycobacterium tuberculosis. Latent tuberculosis infection (LTBI) is defined as a state of persistent immune response to M. tuberculosis antigens without a clinically manifest active tuberculosis. Common to TBC and LTBI is a positive tuberculin skin test (TST) and IGRA test. Quantiferon TB gold test is based on the release of IFN-γ by T-lymphocytes stimulated with Mycobacterium tuberculosis-specific antigens. Research hypothesis: Quantiferon TB gold test is more effective than other diagnostic procedures available in the Republic of Macedonia and will allow rational and proper use of chemoprophylaxis in suspected LTBI in children and will also help in the uncertain diagnosis of active TB. Purpose of the research: To prove the practical application of Quantiferon TB gold test in the diagnosis of active TB and LTBI and its contribution to the decision on chemoprophylaxis in children with LTBI. To determine its values in children of different ages with active TBC or LTBI, its sensitivity and specificity, and the correlation with TST. Material and Methods: We analyzed 100 patients examined for possible M. tuberculosis infection or disease at the Institute of Respiratory Diseases in Children, Kozle, Skopje, as well as a control group of 33 healthy children. The following parameters were analyzed: demographic characteristics, history of exposure to active tuberculosis, presence of BCG vaccination scar, Chest X-ray findings, direct samples of acid-alcohol-resistant bacilli of sputum, Löwenstein-Jensen culture, tuberculin skin test according to Mantoux and the value of IFN-γ according to the Quantiferon TB gold test. Patients are divided into three groups: children with suspicion of LTBI (n = 64), children with suspicion of active TB (n = 36) and a control group of healthy children (n = 33). Statistical data processing: the results were processed by standard statistical methods, using the statistical software IBM SPSS Statistics® 23. From the analyzed variables, a database was created, and it was systematically analyzed. Results: Children with LTBI and active TBC had significantly higher levels of IFN-γ than healthy controls. Also, children with active TB had significantly higher values of IFN-γ, as well as a larger diameter of TST induration compared to those with LTBI. The IFN-γ test for the cutoff of 0.35 IU / mL had 64 % sensitivity and 100 % specificity for the detection of LTBI. Regarding to the active TBC, we received a higher sensitivity of 80.6 % and 100 % specificity. We established a new cut-off value of IFN-γ ≥ 0.252 IU / mL for discrimination between healthy controls and LTBI with 82.4 % sensitivity and 81.8 % specificity, and a value of IFN-γ ≥ 0.822 IU / mL for discrimination between LTBI and active TBC. TST had low sensitivity for detection of LTBI (50 %) and high sensitivity for detection of active TBC (91.7 %). The results showed a positive correlation between the diameter of TST induration and levels of IFN-γ, with a high level of significance. The highest percentage of the matching of the positive results of the two tests was in the group of children with active TBC (77.8 %). Children with close contact had significantly higher levels of IFN-γ and higher TST induration in relation to those with distant contact. Conclusion: Determination of IFN-γ together with TST has a great contribution in more accurate diagnosis of TBC and LTBI in childhood and in the decision on chemoprophylaxis.