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.