Objective: To investigate the prevalence of latent tuberculosis (TB) infection (LTBI), and to identify the risk factors in close contacts of pulmonary TB patients among non-resident population in Shanghai.
Methods: The study subjects were the close contacts of pulmonary TB patients among non-resident populations in Xuhui, Minhang and Songjiang Districts in Shanghai from 2013 to 2014.Questionnaire interview was applied to collect the socio-demographics, TB-related clinical and TB exposure information from the enrolled TB patients and their close contacts. The T-SPOT.TB test was used to identify the infection of M. TB. LTBI was defined as a positive T-SPOT.TB result inthe absence of signs and symptoms related to TB.
Results: In total, 182 pulmonary TB patients and 360 close contacts were enrolled in the present study. The mean age of the close contacts was (34±14) years(range, 2-83 years), including 160 men and 200 women. The T-SPOT.TB test and TB related examination revealed that 17.2% (62/360) of the close contacts were latently infected with M. TB. All the LTBI subjects were household contacts (χ(2)=16.814, P<0.001). In multivariate analysis, the risk of LTBI was statistically associated with the presence of TB symptoms of the index case (OR=2.696, 95%CI: 1.060-6.857) and duration of exposure (OR=1.007, 95%CI: 1.001-1.014); whereas there were no statistically significant associations among age, gender, diagnostic delay of index case, environment of contact place and the risk of LTBI among the studied close contacts.
Conclusions: The prevalence of LTBI in close contacts of pulmonary TB patients among non-resident population in Shanghai is 17.2%.Contact with patients with TB symptoms and longer duration of exposure might increase the risk of LTBI.