A study on prevalence of latent tuberculosis in prison inmates of a single outdoor prison in central Sri Lanka

<b>Background:</b> Latent tuberculosis(LTBI) is an immunological reaction, stimulated by exposure to Mycobacterium tuberculosis antigens with no evidence of active tuberculosis. Prevalence of Tuberculosis is 100 times more in prison inmates than in general population. This study was conducted in a single outdoor prison in central Sri Lanka to estimate the prevalence of LTBI among prison inmates. <b>Methodology:</b> A descriptive cross sectional study conducted in a single outdoor prison from September 2019 to February 2020 where inmates spend about 16 hours a day outdoors. Data were gathered using a questionnaire. Active TB, past TB and prior exposure to tuberculin skin test were excluded. Tuberculin skin test was performed in randomly selected 94 inmates. Data were analyzed using SPSS version 21. <b>Results:</b> 94 men, mean age 38 years, age range 21 to 61 were included in the study.19(20%) had positive mantoux reaction. There were 57 (60.6%) amateur prisoners and 37 (39.4%) with repeated imprisonment. There was no difference in prevalence of LTBI in these two groups(P=0.801). Out of 53 inmates imprisoned more than 6 months 16 (30.2%) had LTBI. Out of 41 (43.6%) who were imprisoned less than 6 months, only 3(7.3%) had LTBI(P=0.089) <b>Conclusion:</b> The prevalence of LTBI, among prison inmates of open prison in central Sri Lanka was 20%, which is less than the figures in general population. There was no association between frequency of imprisonment and duration of prison stay. Although prisons are considered to have high TB burden, outdoor prisons with good ventilation and sun exposure may have contributed to reduce TB infections.