Changes in tuberculin skin test positivity over 20 years in periurban shantytowns in Lima, Peru.

A cross-sectional, community-based study was performed in 2012 with 428 residents of periurban shantytowns in Lima, Peru to study risk factors for and changes in latent tuberculosis infection in age-stratified groups compared with our data from the same region in 1990 (N = 219) and 2005 (N = 103). Tuberculin skin test positivity in these communities was highly prevalent at 52% overall, increased with age (P < 0.01) and was similar to 2005 (53%) and 1990 (48%). From 1990 to 2012, the prevalence of tuberculin positivity decreased in 5-14 and 15-24 year old groups (to 17% and 34%, respectively, both P < 0.05). However, this may be explained by cessation of Bacille Calmette-Guérin revaccination during this period, because Bacille Calmette-Guérin revaccination doubled tuberculin positivity. Over the same 22-year period, tuberculin positivity in the ≥ 25 year old group remained high (71%, P = 0.3), suggesting that prevalent latent tuberculosis infection persists in the adult population despite improving medical care and socioeconomic development in this region.