[Evaluation of the mean annual risk of tuberculosis infection in the town of Conakry].

A study of tuberculous disease was carried out in children aged 5 to 13 years old who were first year pupils in primary schools in the town of Conakry (Republic of Guinae) with a view to determining the annual risk of tuberculous infection. In total 4,198 children distributed throughout 15 schools were tested after first looking for BCG vaccination scars. In the sample tested 1,444 children (34.4%) had vaccination scars and 2,754 (65.6%) did not. Amongst the 1,444 children with BCG scars, 1,367 (94.7%) were reviewed 72 hours after one unit of tuberculin RT 23 to have the skin reaction RDI read. Amongst these 210 (15.4%) had an area of induration greater than 6 m.m. diameter. Amongst 2,754 children who did not have BCG scars 2,655 (96.4%) were reviewed for the reading of the IDR: 330 children (12.8%) had an area of induration greater than 6 m.m. diameter. The percentage of children with an IDR greater than 6 m.m. as well as the mean diameter of induration was significantly greater in the group with a vaccination scar. The age of the children influenced the size of the induration. A factorial analysis revealed at the same time an age factor and a significant scar factor. Calculations from the prevalence of areas of induration with diameter greater than 6 m.m. in non-vaccinated children revealed an annual risk of infection of 1.52. A number of cases of pulmonary tuberculosis with positive microscopy in Conakry town is estimated at 90 per 100,000 inhabitants.