Prevalence of tuberculosis infection and comparison of multiple-puncture liquid tuberculin test and Mantoux test among drug users.

In order to determine the prevalence of latent infection due to Mycobacterium tuberculosis in drug users and to provide centres for drug users with a practical tool for tuberculosis screening, 237 drug users were subjected to the Monotest and, for reference purposes, to the Mantoux test. The overall prevalence of subjects with a tuberculin skin reaction size > or = 5 mm in the Mantoux test was 25.7%; utilizing a cut-off of > or = 10 mm, the prevalence was 11.4%. Irrespective of cut-off, the Monotest showed a sensitivity of > 90% and a specificity of > 80%. At a prevalence of 25.7%, and with cut-offs of > or = 5 or > or = 10 mm, the positive predictive value was 83% or 62.2%, respectively. Irrespective of cut-off, the negative predictive value was > 97%. In conclusion, the Monotest proved satisfactory as a tool for epidemiological screening in a population with a high prevalence for latent tuberculosis, namely drug users.