epidemic and of other factors . schoolchildren : the influence of the HIV Tuberculosis infection and disease among

Background—The HIV/AIDS epidemic has caused an excess of tuberculosis cases in Spain and in other countries, but its impact on tuberculosis infection is less well understood. This study presents a massive screening undertaken to estimate the prevalence of tuberculous infection in a cohort of primary school entrants. The evolution of the risk of infection is studied by comparison with previous data in the same population. Methods—Tuberculin skin test screening with 2TU of PPD RT 23 of first grade students in the primary schools of Barcelona, in the 1994–95 school year (cohort born in 1988). Information was also sought from families of unscreened children. Contacts of PPD+ children were traced to locate index cases. The results were also linked to the case registry of the tuberculosis control programme. Results—The prevalence of tuberculin reactors free of BCG vaccination among the 11 080 schoolchildren screened belonging to the 1988 cohort was 0.76%. A 3% annual decline in the annual risk of infection is estimated by comparison with previous data. The identification of 24 cases with a previous history of tuberculosis disease and of 13 cases with active disease diagnosed after the screening was possible by the follow up of these tuberculin positive children and of the information provided by families of unscreened pupils. The screening detected 1.5 new cases of tuberculosis per 1000 tuberculin tests performed. Tuberculosis infection could be traced to HIV infected tuberculosis cases for at least 6% of the positive schoolchildren. Conclusions—The decline of the annual risk of infection continues in Barcelona, although at a slower pace than before the HIV/AIDS epidemic, probably attributable to the influence of injecting drug users with smear positive tuberculosis and HIV/AIDS. (J Epidemiol Community Health 1999;53:112–117) The human immunodeficiency virus (HIV) infection has caused a clear excess of tuberculosis cases in Spain and in other countries. 2 The evolution of tuberculosis infection is less well understood. Some authors believe that the decline in infection continues, as the excess cases linked to the HIV epidemic is caused by the expression of tuberculosis disease among people who were already infected by Mycobacterium tuberculosis years ago, among whom the acquired immunodeficiency explains the clinical disease. 4 However, a proportion of these cases may be infective, and thus contribute to the dissemination of infection to new population groups. In Spain, the concentration of HIV infection among people who are injecting drug users, 6 many of whom are relatively young and are household contacts of children, could promote this infection pathway. In this context, monitoring the evolution of infection and disease becomes crucial to understand current changes. This is why this study was undertaken, based on the tuberculin screening of schoolchildren in the months of January to May 1995, during the first year of mandatory schooling (first grade, when pupils are 6–7 years old). Universal BCG vaccination was interrupted in Catalonia and in Barcelona from 1976, so that current schoolchildren are free of BCG interference when submitted to the tuberculin test, except for a few born in other areas where BCG is used. Universal screening in first grade was interrupted in Barcelona in 1989 as less than 1% of the children tested were positive. A first grade screening policy was kept for schools located in neighbourhoods considered to be at higher risk because of social and health criteria. To monitor the evolution of infection, universal screening of first graders was done in 1992. Its results suggested that infection prevalence kept declining, but at a slower pace than previously estimated. The comparison with previous studies was obscured by changes in tuberculin supply, as the Comité d’Experts en Tuberculosi (Catalan Expert Committee on Tuberculosis) recommended in 1989 the use of 2 TU of PPD RT 23 instead of the 5 TU previously used. This paper reports the results of a second universal screening with 2 TU of PPD RT 23, performed three years later, whose objectives are to assess the evolution of tuberculosis infection, and to clarify the status of those children not tested because parents explicitly denied permission for the test. The contribution of school-based screening to the identification and control of sources of infection is also evaluated, after a tuberculosis control programme has been in operation for 10 years. Methods Tuberculin skin tests were performed with 2 TU of PPD RT-23, in 0.1 ml of liquid solution and stabilised with Tween 80, in accordance J Epidemiol Community Health 1999;53:112–117 112 Institut Municipal de Salut Pública, Barcelona City Health Department, Spain