High utility of contact investigation for latent and active tuberculosis case detection among the contacts: a retrospective cohort study in Tbilisi, Georgia, 2010-2011.

Setting: The study was conducted at the National Center for Tuberculosis and Lung Diseases (NCTBLD) in Tbilisi, Georgia.
Objective: To assess the utility of contact investigation for tuberculosis (TB) case detection. We also assessed the prevalence and risk factors for active TB disease and latent TB infection (LTBI) among contacts of active pulmonary TB cases.
Design: A retrospective cohort study was conducted among the contacts of active pulmonary TB cases registered in 2010-2011 at the NCTBLD in Tbilisi, Georgia. Contacts of active TB patients were investigated according to an "invitation model": they were referred to the NCTBLD by the index case; were queried about clinical symptoms suggestive of active TB disease; tuberculin skin testing and chest radiographs were performed. Demographic, laboratory, and clinical data of TB patients and their contacts were abstracted from existing records up to February 2013.
Results: 869 contacts of 396 index cases were enrolled in the study; a median of 2 contacts were referred per index case. Among the 869 contacts, 47 (5.4%) were found to have or developed active TB disease: 30 (63.8%) were diagnosed with TB during the baseline period (co-prevalent cases) and 17 (36.2%) developed active TB disease during the follow-up period (mean follow up of 21 months) (incident TB cases). The incidence rate of active TB disease among contacts was 1126.0 per 100,000 person years (95% CI 655.7-1802.0 per 100,000 person-years). Among the 402 contacts who had a tuberculin skin test (TST) performed, 52.7% (95% CI 47.7-57.7%) had LTBI.
Conclusions: A high prevalence of LTBI and active TB disease was found among the contacts of TB cases in Tbilisi, Georgia. Our findings demonstrated that an "invitation" model of contact investigation was an effective method of case detection. Therefore, contact investigation should be scaled up in Georgia.