Multi-centre study on the prevalence of latent TB infection among inmates in Spanish prisons

Aims: To study the prevalence of latent tuberculosis infection (LTBI) amongst inmates in Spanish prisons. Materials and Methods: Multi-centre, cross-sectional study; two stage sampling. Socio-demographic, prison and clinical variables were gathered. A univariate, bivariate and multivariate analysis was carried out using logistic regression with the variables that showed statistical significance. The odds ratio was calculated with a confidence interval of 95%. Results: 378 patients. The Mantoux test (PPD) assessable in 90.2% was available. 91.2% men, 37.8% foreigners with average age of 35.9±10.3 years. Average stay in prison: 2 years, 28.7% had been > 5 years in prison. 49.6% entered prison in 2006 or before. 24.5% had a history of intravenous drug use (IDU). 50.4% presented LTBI that was associated with: age > 40 years (63.2 vs. 43.8%; CI: 1.39-3.49; OR: 2.20; p=0.001); stay of > 5 years in prison (71.2 vs. 41.3%; CI: 2.13-5.75; OR: 3.50; p<0.001); in prison since 2006 or before (58.1 vs. 42.6%; CI: 1.22-2.88; OR: 1.87; p=0.004); infected with HCV+ (66.3 vs. 45.3%; CI: 1.40-4.0; OR: 2.37; p=0.001). The logistic regression model confirmed the independent association of LTBI with: a) age > 40 years (OR: 1.76; CI: 1.08-2.87; p=0.024); and length of prison stay > 5 years (OR: 2.50; CI: 1.41-4.43; p=0.002). Conclusions: The prevalence of LTBI in prison is very high, especially amongst inmates over 40 and those who have been in prison for more than five years. To prevent the risk of progression to tuberculosis, treatment is recommended for those who require it along with the maintenance of control programmes for this pathology.