1666. Yield of Tuberculosis Contact Tracing among Veterans after Outpatient Exposure

BACKGROUND: Tuberculosis contact tracing (TBCT) is essential to detecting transmission. High priority contacts for TBCT include children less than 5 and those with prolonged, close contact with a tuberculosis (TB) case. Other populations considered high priority include those with certain comorbidities. While data are limited, there is evidence for transmission in outpatient settings with short duration/casual contact. We describe the yield of TBCT among a high priority cohort after exposure in to active TB in VA clinics. METHODS: Between 2016-2019, VA Northern California performed 4 episodes of TBCT in the outpatient setting. In TBCT 1, the index case was an AFB smear positive healthcare worker (HCW) with 30-minute patient appointments. In TBCT 2-4, the index cases were patients, 2 of whom were AFB smear positive. TBCT included patients seen by the HCW (TBCT 1) and those with appointments one hour before or after the index patient in the same clinic (TBCT 2-4). Contacts were offered interferon-gamma release-assay (IGRA). Staff contacts were tested by purified protein derivative (PPD). Comorbidities, prevalent and new cases with positive TB testing were calculated and compared between different groups. RESULTS: Fifty-one percent of veteran contacts had comorbidities placing them in a high priority group for TBCT. Among the 593 patients who had an IGRA during TBCT, 40 (6.7%) tested positive. Twenty-six (4.4%) had no known history of prior positive TB test of whom 6 reported a previous TB exposure history. Veterans exposed to the HCW did not have a higher prevalence of IGRA positivity or a new positive IGRA compared to TBCT 2-4 (5.5% vs 8.0%, p-value 0.22 and 3.4% vs. 5.3%, p-value 0.26). Among the 130 staff tested in TBCT 1-4, one (0.7%) converted during TBCT 1. CONCLUSION: After extensive TBCT, the prevalence of latent TB among short duration/casual contacts of TB was 6.7%, similar to the baseline prevalence of latent TB of 6% in California. In this high priority population for TBCT, no difference was seen when there was face-to-face contact versus a shared waiting room with the index case. Staff conversion rate was extremely low. While decisions to perform TBCT in outpatient settings need to be individualized, the yield of TBCT in this population of veterans was low. DISCLOSURES: All Authors: No reported disclosures