Background: This cross-sectional study was conducted to assess the prevalence of and identify factors associated with latent Mycobacterium tuberculosis (MTB) infection in prisoners of North West Frontier Province (NWFP).
Methods: A stratified random sampling technique was used to select a sample of 425 from a total of 6607 male prisoners aged 18-60 years from the five central prisons of NWFP, Pakistan (Peshawar, Dera Ismail Khan, Haripur, Kohat, and Mardan). The selected inmates were interviewed using a structured pre-tested questionnaire; a Mantoux tuberculin skin test (TST) was also performed. Latent MTB infection status of the prisoner was determined by the size of the induration of the TST in the presence/absence of a previous BCG scar.
Results: Overall prevalence of latent MTB infection among prisoners was 48% (204/425). Using multiple logistic regression, a prisoner's age, educational level, smoking status, duration of current incarceration, and average accommodation area of 60 ft(2) or less in prison barracks were found to be statistically significant (P < 0.05) predictors of latent MTB infection.
Conclusion: The high prevalence of latent MTB infection as assessed by TST in prisoners requires immediate steps be taken to identify and confirm MTB infection, and to treat and counsel those found to be positive in this setting. Efforts to halt MTB transmission in prisons should include: routine screening of prisoners on entry using sputum smear and TST for diagnosis of tuberculosis (TB) and latent MTB infection, respectively. The isolation and treatment of TB positive prisoners and chemo-prophylactic treatment of TST positives, reduction of overcrowding, education regarding the harmful effects of smoking, and intensive monitoring of those serving longer prison terms may help reduce the MTB transmission in this setting and in the community at large.