A total of 45 diagnosed TB patients from each of 7 Shanghai districts were chosen and approximately 3 contacts per case were randomly selected. A structured questionnaire was used to acquire socio-demographic information and to assess the degree of exposure to index cases. LTBI screening was performed by T-SPOT.TB assay.
Of 969 enrolled contacts, 39%were men, average age was 45聽卤聽19.1 years, and 76.3%were household contacts. LTBI was identified in 29.6%of subjects. Those contacting smear-positive TB patients were 2.24 times (95%CI, 1.586-3.162) more likely to develop LTBI than those otherwise; household contact significantly increased the likelihood of LTBI by 1.52 times (95%CI, 1.061-2.180). Furthermore, among household contacts, the risk of LTBI was higher in spouses and first-degree relatives and increased with age and contact duration.
A high prevalence of LTBI was observed among the TB contacts in Shanghai, highlighting the need of intervention among the household contacts and those contacting smear-positive TB patients.