Incidence of tuberculosis among a cohort of tuberculin-positive refugees in Australia - Reappraising the estimates of risk

Estimates of the lifetime risk of tuberculosis have varied widely and may n ot be applicable in all current settings. The aim of this study was to meas ure the incidence of reactivation of latent tuberculosis in a cohort of 15, 489 predominantly Southeast Asian refugees aged 12 yr and over who arrived in Sydney, Australia during the period 1984 to 1994 and who had a clear che st X-ray on arrival. Tuberculin skin test (TST) reaction size and the prese nce of a BCC scar were recorded at entry. Incident cases of tuberculosis, o ccurring before June 1998, were identified by record linkage analysis with confirmatory review of case notes. There were 122 cases of tuberculosis ove r an average 10.3 yr of follow-up (crude annual incidence, 76.2/100,000). T here was a linear increase in risk with increasing TST reaction size above 10 mm. The risk, and the relation of risk to TST reaction size, were unrela ted to BCC scar status. Among those whose initial TST reaction was greater than or equal to 15 mm, the annual incidence rate in the first 3 yr was 213 (95% CI, 150 to 300) per 100,000 person-years and in the subsequent 10 yr the rate averaged 122 (95% CI, 90 to 165) per 100,000 person-years. The obs erved rates are similar to those estimated in the general population of the United States in the 1950s and 1960s. Further data on the prognosis of tub erculosis and the effects of isoniazid preventive therapy in Southeast Asia n migrants to Western countries are required to inform policy and practice for the prevention of tuberculosis in this population.