Risk factors for tuberculosis infection and disease.

We conducted a prospective study among patients with newly diagnosed pulmonary tuberculosis and their close contacts to identify clinical and socio-economic risk factors for tuberculosis infection and disease. Ninety patients and 277 contacts were enrolled. The prevalence of infection was 45% [95% confidence interval (CI): 39-51%] among contacts. Factors like age, gender, race, delay of diagnosis and treatment, presence of cavitation in chest radiograph, cough, unwillingness to cover the mouth, volume of air shared by close contacts and patients were investigated. Inclusion of all these factors in a multivariate logistic regression model showed that only delay in diagnosis is significantly associated to the increase of prevalence (p < 0.0002), documenting that delay in diagnosis of the case is a crucial factor for tuberculosis infection and/or disease.