positive from negative individuals. A study from the University of Southampton shows that variations in environmental temperatures can have a profound effect on the performance of IGRA. A recently published study from the same group also provided evidence that immunosuppressive agents significantly impair the performance of IGRAs, raising concerns about their reliability in immunosuppressed patients. Although, IGRA replaced the TST in most of the clinical settings but the variability is a concern while reading the result Tuberculosis detection using trained rats The international nonprofit organization APOPO has been working with Sokoine University of Agriculture in Tanzania to train African giant pouched rats (Cricetomys ansorgei) to detect the "scent" of tuberculosis. A recent study shows that "rats increased pediatric tuberculosis detection by 67.6%" and that training these creatures could help address the current challenges related to the diagnosis of this illness in children. Tuberculosis classification system used in the US The current clinical classification system for TB (Class 0 to 5) is based on the pathogenesis of the disease. The U.S. Citizenship and Immigration Services has an additional TB classification (Class A, B1, or B2) for immigrants and refugees developed by the Centers for Disease Control and Prevention (CDC). The (Class) B notification program is an important screening strategy to identify new arrivals who have a high risk for TB. References Further reading Notes Medical Examination of Aliens (Refugees and Immigrants) - Division of Global Migration and Quarantine, CDC (website). Targeted Tuberculin Testing and Treatment of Latent Tuberculosis Infection 2000 ATS/CDC (fulltext, PDF format) (Updates 2001–2003). External links University of Washington Molecular Diagnosis, Microbiology Division | PCR-based detection in direct tissue samples Oxford Immunotec Medical Diagnostics|TB Education and Learning Zone Spoligo typing kits (Ocimum Bio Solutions) for detection of TB Tuberculosis Respiratory system procedures