Indices to Measure Magnitude of TB Problem
Routine statistics
Mortality, Incidence and Prevalence: Often unreliable, however, useful to know the trend.
In and out patients statistics: Useful to know rough idea on prevalent diseases.
TB prevalence survey
Useful to know the prevalence and the programme coverage.
Difficult to know the incidence. High cost.
Annual risk of TB infection (ARTI)
Obtained from the tuberculin survey.
Constraints: High coverage of BCG vaccination
Relation Between ARTI and Other Epidemiological Indices
Incidence of Smear (+) PTB per 100,000 = ARTI(%) (50〜60)
Incidence of TB Meningitis among children of 0〜4 years of age per 100,000 = ARTI(%) × 5
If no effective treatment (natural history),
Mortalaity from TB per 100,000 = (1/2) × Incidence of Smear (+) PTB
Prevalence of Smear (+) PTB per 100,000 = 2 × Incidence of Smear (+) PTB
Magnitude of Global TB Problem
Number infected 1.9 billion
Number of annual new TB cases 8 million
Number of annual death from TB 3 million
TB is a biggest killer among infectious diseases in the adult.
TB is a heavy burden for developing countries.
95% of new TB cases and 99% of TB death are seen in developing counries.
