Incidence of TB in a community is measured by

Epidemiological indices of TB Incidence of TB infection (Annual infection rate, Annual risk of infection - ARI) : percentage if population understudy who will be newly infected with TB among Non-infected in 1 year Express attacking force of TB in community In developing countries 1% ARI corresponds to : 50 SS +ve cases per 100000 general population. Tuberculin conversion index is the best indicator for evaluation of TB problem and its trend ' in the community Prevalence of TB infection Percentage of individuals who show a positive reaction to standard Tuberculin test. Represent cumulative experience of population in' recent as well as remote infection' with TB Tuberculin test is the only way of estimating the prevalence of infection in a population Incidence of disease Percentage of new TB cases per 1000 population. Reveals trend of problem, including impact of control measures. Is of utility only in countries where high propoion of new cases are detected and notification is reliable Sputum smear examination (AFB) is a reliable method for estimation. Prevalence of disease or case rate Percentage of individuals whose sputum is positive for TV bacilli on microscopic examination Best available practical index to estimate case load in community. Age specific prevalence is most relevant index Ref: Park 25th edition Pgno : 219-220