The study is a prospective study to improve the diagnosis and management of latent TB in HIV-infected and HIV uninfected children in Thailand. The objectives are to assess the sensitivity and specificity of IGRAs (T-Spot®.TB, a T-cell-based assay, and QuantiFERON®-TB Gold In-tube, a whole blood assay), TST, and a refined symptom-based questionnaire in diagnosing latent TB in 166 HIV-infected and HIV uninfected children in Thailand, and to evaluate the influence of age, nutritional and immune status on children's response to the IGRAs. These children will be screened for TB with a detailed TB contact history, symptom-based questionnaire, physical examination, TST, chest radiograph (and abdominal ultrasound for those with abdominal symptoms), IGRAs, and clinical specimens for acid fast bacilli stain and culture. A diagnostic algorithm will be generated using the combination of test modalities with the highest sensitivity and specificity results.