Abstract 1

1 Preventable Tuberculosis Cases Arising from Contacts to Pulmonary Cases in New York City Holly Anger, Douglas Proops, Tiffany Harris, Shama Ahuja New York City Department of Health and Mental Hygiene Rationale: Contacts to infectious tuberculosis (TB) patients are at high risk for TB disease. Contact screening for identification of latent TB infection (LTBI) and treatment of LTBI (TLTBI) are key components of TB control; however, little data exist regarding the longitudinal impact of these interventions within a TB control program setting. Methods: Using surveillance data, we identified TB cases arising from contacts with a positive tuberculin skin test (TST) result performed as part of contact investigation to 5144 pulmonary TB patients diagnosed in New York City (NYC), 1997—2003. We defined an incident TB case as a contact diagnosed with active TB at least 8 weeks after testing TST-positive through 12/31/2007. We calculated TB incidence rates (IRs) stratified by TLTBI completion. To estimate the proportion of cases that may have been prevented by TLTBI, we calculated the attributable risk percent for TLTBI initiation and completion. We estimated the number of cases prevented by TLTBI by comparing the observed number of incident cases to the expected number that would have occurred had no contacts started TLTBI. Results: A TST was performed for 25,364 /29,769 (85%) contacts and 7941 (27%) were TSTpositive. After excluding 185 contacts diagnosed with active TB within 56 days of the positive result, incident TB occurred in 81/7756 (IR=140/100,000) contacts, including 40/1662 (IR=334/100,000) who never started TLTBI, 20/2195 (IR=119/100,000) who started but did not complete TLTBI, 19/3754 (IR=68/100,000) who completed TLTBI, and 2/145 (IR=187/100,000) who discontinued TLTBI due to adverse reactions. The TLTBI initiation rate was 79% and of those initiating, 62% completed. Preventable cases occurred in 29/40 (72%) cases who never initiated TLTBI and 8/20 (41%) cases who started but did not complete TLTBI. If none of the TST-positive contacts had started TLTBI, the expected number of TB cases would be 187, leading to an estimated 106 cases that were prevented among NYC contacts. Conclusions: A large proportion of TB cases arising from infected contacts to NYC TB cases may have been prevented with TLTBI. Even with a low TLTBI completion rate, a substantial number of TB cases were prevented by provision of TLTBI to infected contacts.