title: Change in the risk of tuberculous infection over an 8-year period among schoolchildren in Bangalore City.
abstract: METHODS
  Bangalore City, South India.
  
  
  OBJECTIVE
  To estimate the trends in transmission of tuberculous infection.
  
  
  METHODS
  Two tuberculin surveys were carried out among children attending grades 1 and 2 of 60 selected schools at an interval of 8.3 years, corresponding to the period of DOTS expansion. Tuberculin testing was carried out using 1 tuberculin unit (TU) of purified protein derivative (PPD) RT 23 with Tween 80, and the maximum transverse diameter of induration was recorded about 72 h later. As the reactions due to infection with tubercle bacilli could not be clearly delineated from cross-reactions on the frequency distributions of tuberculin reaction sizes at either survey, the prevalence of tuberculin reactions > or = 10 mm, > or = 12 mm and > or = 14 mm in size were compared between the two surveys. The annual risk of tuberculous infection (ARTI) was computed from the estimated prevalence of reactions > or = 14 mm in size.
  
  
  RESULTS
  Estimates of prevalence of reactions at all chosen cut-off points were lower at Survey II compared to Survey I. These differences were statistically significant. An average per annum decline in ARTI of about 4% was observed between the two surveys.
  
  
  CONCLUSIONS
  Tuberculosis control measures should be further intensified to enhance the rate of decline in transmission of infection.
authors.affiliation: National Tuberculosis Institute, Bangalore, India. vin_chadha@rediffmail.com
authors.forename: V K
authors.initials: VK
authors.lastname: Chadha
authors.forename: R
authors.initials: R
authors.lastname: Jithendra
authors.forename: P
authors.initials: P
authors.lastname: Kumar
authors.forename: R
authors.initials: R
authors.lastname: Kirankumar
authors.forename: A N
authors.initials: AN
authors.lastname: Shashidharan
authors.forename: P
authors.initials: P
authors.lastname: Suganthi
authors.forename: J
authors.initials: J
authors.lastname: Gupta
authors.forename: P S
authors.initials: PS
authors.lastname: Jaganath
mesh_terms: D001500:BCG Vaccine / Q000008:administration & dosage; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D018570:Risk Assessment; D012494:Sampling Studies; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology* / Q000517:prevention & control
chemical_list: D001500:BCG Vaccine