Annual risk of tuberculosis infection in a rural population of South India and its relationship with prevalence of smear positive pulmonary tuberculosis.
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Date
2013-10
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Abstract
Background: We conducted a tuberculin survey to estimate the annual risk of tuberculous infection (ARTI) among children
in a sub-division of rural Bangalore district. A TB disease survey was conducted in the same area around the same time and
has already been published. DOTS strategy is being implemented in the study area since 2002.
Methods: The tuberculin survey was conducted during 2010-2011 among 3838, 5-9-year-old children attending 147 schools
selected by simple random sampling. Children were tuberculin tested with 2TU PPD RT23 with Tween 80 and maximum
diameter of induration was measured between 48-96 hours. ARTI was computed from prevalence of infection estimated by
mirror-image technique. Prevalence of smear positive pulmonary TB estimated during the disease prevalence survey in
2008-10 was used to find out its relationship with ARTI.
Results: Using the observed mode of tuberculin reaction sizes at 19 mm, among surveyed children, prevalence of infection
was estimated at 7.3% (CI: 6.5-8.1); ARTI was computed at 1.05%. Considering the mean age of children, estimated ARTI
most closely approximated to the year 2008. Every one per cent ARTI was found to correspond to a prevalence of 103
sputum smear positive patients of PTB, which was similar to the ratio of 106 found in the same study area during 1960s.
Conclusion: There has been no change in the relationship between ARTI and prevalence of smear positive pulmonary TB from
the pre-DOTS era and thus in the number of children infected by each adult point prevalent case of smear positive pulmonary
TB each year suggesting the need for early case detection and treatment.
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Keywords
Tuberculosis, Infection, Risk, Annual, Prevalence, India
Citation
Chadha V K , Anjinappa Sharada M, Gowda Umadevi, Srivastava Ramesh, Ahmed J, Kumar Prahlad. Annual risk of tuberculosis infection in a rural population of South India and its relationship with prevalence of smear positive pulmonary tuberculosis. Indian Journal of Tuberculosis. 2013 Oct; 60(4): 227-232.