Influence of hospitalization upon diagnosis on the risk of tuberculosis clustering

Setting: Culture-positive tuberculosis (TB) diagnosed in the metropolitan area of Milan (Italy) over a 5-year period (1995-1999). Objective: To assess the impact of short-course hospitalization upon diagnosis on the overall risk of TB clustering. Design: Restriction fragment length polymorphism profiles with a similarity of 100% defined a cluster. Uni- and multivariable logistic regression models were performed to assess factors associated with clustering. Results: Among 1139 patients, 392 (34.4%) were hospitalized before or soon after diagnosis, 405 (35.6%) received domiciliary treatment since the diagnosis and 392 (30%) had no information about initial clinical management. One hundred fifteen molecular clusters involving 363 patients were identified. Using multivariable analysis, hospitalization was not significantly associated with clustering (OR 1.06, 95%CI 0.75-1.50, p=0.575). Subjects aged >65 years old (OR 0.60; 95CI%:0.37-0.95; p=0.016) and non-Italian born patients (OR 0.56; 95%CI:0.41-0.76; p<0.001) were running a lower risk of clustering. Conversely, HIV co-infected patients (OR 1.88, 95%CI:1.20-2.95, p=0.006) and those with MDR TB (OR 2.50, 95%CI:1.46-4.25, p=0.001) were significantly more likely to be involved in clusters. Conclusion: In our cohort, domiciliary treatment was not associated with TB clustering. Expanding domiciliary treatment upon diagnosis appears as an advisable measure to reduce unnecessary costs for the health care system.