Trend in tuberculous meningitis in Barcelona in children aged 0–4 years: correlation with the annual risk of tuberculous infection

Abstract

Setting: All the paediatric hospitals in the province of Barcelona. Objective: To examine the trend in the incidence of tuberculous meningitis (TM) in children aged 0–4 years and its correlation with the annual risk of tuberculous infection. Design: Survey conducted between 1975 and 1991. Results: 157 cases of TM in children aged 0–4 years were diagnosed between 1975 and 1991. A constant decrease during the prospective period is observed from 21 cases of TM in 1977 to only 2 cases in 1991 with an annual decrease of 5.5%, which is smaller than the 8% annual decrease of the annual risk of tuberculous infection. A close correlation between the observed incidence of TM and the average annual risk of infection to which children in the same area were exposed r = 0.9156 ( P < 0.0001) is verified. Moreover, this correlation gets even closer when considering the annual risk of infection as a percentage of the TM incidence, since a stable correlation of about 1% (0.89–1.39%) is demonstrated. Nevertheless, the incidence and the number of observed cases of TM is twice that expected if one refers to the Table that calculates meningitis cases by means of the annual risk of infection. We observed one case of TM among 218–384 infected children, i.e. a risk of developing TM of 0.19–0.26%, higher than that found in the countries with the most favourable tuberculosis situations. The sharp decrease of TM coincides with the suppression of BCG-vaccination in Barcelona, which suggests that it has not substantially changed the decrease of the risk of developing TM in children under 5 years of age. The decrease in the annual risk of infection, and consequently TM, is essentially due to the improvement of treatment in adults. Conclusion: It is confirmed that the incidence of TM in children under 5 years represents 1% of the annual risk of infection. The TM incidence thus permits the determination of the annual risk of infection when the conditions to calculate it directly do not exist.