Only a few risk factors for tuberculosis given infection have been discussed in the previous slides. This one summarizes them and adds some others. Hollow circles are odds ratios, i.e., estimates arrived at from retrospective studies. Filled circles are relative risks, i.e., estimates arrived at from population-based studies. Two circles connected by a dotted line indicate availability of more than one study and the range of the estimates.
This ends the presentation on the etiologic epidemiology of tuberculosis.
Before you continue, you might wish to reflect on the following. If you had to rate the public health importance of risk factors on a global scale, which of the above factors would you consider the most and which the least important?
The public health importance of a risk factor depends on the strength of the factor, but even more importantly on its prevalence in the population. Jejunoileal bypass surgery is a very strong risk factor but it is rare that a patient undergoes this presentation which is usually reserved for persons with excessive body weight that cannot be controlled anymore in any other way. While individually important, it is thus a negligible contributor to global tuberculosis incidence.
Conversely, recent infection is a frequent event: almost always whenever a new cases of infectious tuberculosis arises, this case will have transmitted already tubercle bacilli to another person before the diagnosis is made and chemotherapy arrests transmissibility. HIV infection is the strongest yet identified risk factors for progression of latent infection with M tuberculosis to tuberculosis and in many, but not all parts of the world, it is also highly prevalent in the general population. It is certainly, the most important risk factor in many African countries, but it is of virtually no importance for instance in Bangladesh. |
