Prevalence of positive tuberculosis skin tests during 5 years of screening in a Swiss remand prison

BACKGROUND: Tuberculosis (TB) screening in prisons is recommended, but the appropriate methods remain controversial. Studies evaluating screening in remand prisons arc scarce. METHOD: Between 1997 and 2001, voluntary screening based on the tuberculin skin test (TST) was offered to all prisoners on entry into the largest remand prison in Switzerland. Prisoners with positive results underwent chest X-rays. We analysed this information collected in an anonymous database. RESULTS: A total of 4890 prisoners entered the prison and were eligible for screening; 3779 (77.3%) had TST performed on average 9 days after arrival: 46.9% were positive (induration >= 10 mm). Positive TST rates were similar over the 5 years. Women were more likely to have a negative TST (60.4%) than men (47.7%; P < 0.001, Pearson's chi(2) 16.5). Positive TSTs varied according to the prisoner's country of origin (64% for sub-Saharan Africa, 57% for Eastern Europe, 56% for North Africa, 51% for Asia and 34% for North and West Europe). CONCLUSION: The percentage of TST-positive subjects was high, and most did not receive preventive treatment for latent TB. The usefulness of systematic TST for all prisoners on entry is limited, as diagnosis of TB disease usually remains the priority in prisons. Keywords

Detection of latent tuberculosis in immunosuppressed patients with autoimmune diseases: performance of a Mycobacterium tuberculosis antigen-specific interferon gamma assay

OBJECTIVE: To analyse the performance of a new M. tuberculosis-specific interferon gamma (IFNgamma) assay in patients with chronic inflammatory diseases who receive immunosuppressive drugs, including tumour necrosis factor alpha (TNFalpha) inhibitors. METHODS: Cellular immune responses to the M. tuberculosis-specific antigens ESAT-6, CFP-10, TB7.7 were prospectively studied in 142 consecutive patients treated for inflammatory rheumatic conditions. Results were compared with tuberculin skin tests (TSTs). Association of both tests with risk factors for latent M. tuberculosis infection (LTBI) and BCG vaccination were determined and the influence of TNFalpha inhibitors, corticosteroids, and disease modifying antirheumatic drugs (DMARDs) on antigen-specific and mitogen-induced IFNgamma secretion was analysed. RESULTS: 126/142 (89%) patients received immunosuppressive therapy. The IFNgamma assay was more closely associated with the presence of risk factors (odds ratio (OR) = 23.8 (95% CI 5.14 to 110) vs OR = 2.77 (1.22 to 6.27), respectively; p = 0.009), but less associated with BCG vaccination than the TST (OR = 0.47 (95% CI 0.15 to 1.47) vs OR = 2.44 (0.74 to (8.01), respectively; p = 0.025). Agreement between the IFNgamma assay and TST results was low (kappa = 0.17; 95% CI 0.02 to 0.32). The odds for a positive IFNgamma assay strongly increased with increasing prognostic relevance of LTBI risk factors. Neither corticosteroids nor conventional DMARDs significantly affected IFNgamma responses, but the odds for a positive IFNgamma assay were decreased in patients treated with TNFalpha inhibitors (OR = 0.21 (95% CI 0.07 to 0.63), respectively; p = 0.006). CONCLUSIONS: These results demonstrate that the performance of the M. tuberculosis antigen-specific IFNgamma ELISA is better than the classic TST for detection of LTBI in patients receiving immunosuppressive therapy for treatment of systemic autoimmune disorders.