The Use Of T-SPOT.TB Assay In The Tuberculosis High-risk Children

Background: The clinical manifestations of tuberculosis are diverse, and can be involving all systems. Especially latent tuberculosis infection(LTBI) become very often conceals. These aspects bring great difficulties for clinical diagnosis. As far,the tuberculin skin test is the only diagnosis method of LTBI in children. However, because of many defects, it caused very high "false positive" rate in the areas where BCG being vaccinated common[1]. In addition, there are certain subjective dependence in operation and results's explaination of the skin test, which reduced its accuracy[2]. Enzyme-linked immunospot assay for interferon-γbased specific antigen is a new method of diagnosis of tuberculosis which enzyme-linked immunosorbent spots technology being applicated. 0bjective: To explore the value of T-SPOT.TB assay in monitoring the tuberculosis high-risk Children, provide the basis for early treatment and management in the latent tuberculosis infection children.Methods:①Participants 47 children who had close contact with the index cases with smear positive active TB, but did not have signes of active TB themselves were recruited from January to September 2009.②Group 19 were male, 28 girls. They were 4 months to 14 years old, the average age being 5.75±3.94 years. They were divided into four groups by their induration of PPD. All subjects were collected peripheral venous blood 2.5mL in room temperature.③All children were tested with T-SPOT.TB and PPD at 0, 6, 12, 18 and 24 months. During this time they were monitored for sings of active TB diesease. If necessary, chest radiography. AT the last,the number of spots are observed after treatment; And then we also analyzed the various factors of the test.Results:①26/47 (55.3%) children were positive by PPD. 6/47 (12.7%) were positive by the T-SPOT.TB assay. PPD results were grouped according to size of induration, T-SPOT.TB positivity varied between the four groups, P=0.002 indicating that subjects with a larger PPD result were more likely too have LTBI; After anti-tuberculosis treated for 6 months, the T-SPOT.TB result became negative in 4 cases while the number of spots was significantly reduce in 2 cases, After 12 months all were negative.②After BCG being vaccinated, the average diameter of PPD induration fluctuates between 0 and 15mm. In the case of can not get the gold standard, T-SPOT.TB positivity was 10% in the group with a PPD between 10 to 15mm T-SPOT.TB positivity was 100% when the PPD induration was greater than 16mm (Table 3).Conclusion: Among the tuberculosis high-risk children, The T-SPOT.TB assay could have a more specific value for diagnosis and indentification of LTBI than PPD test, and the effect can be assessed, PPD test can be used Initial screening for LTBI. The results of the T-SPOT.TB assay had little relationship with sex, age, BCG vaccination status, history of exposure to source case, immunity state, induration diameter of PPD, infection position.