753. Screening for Latent Mycobacterium tuberculosis Infection (LTBI): A Clinical Conundrum of Public Health Concern

BACKGROUND: Tumor necrosis factor (TNF)-α inhibitors increase the risk of reactivating LTBI, hence screening is crucial prior to starting therapy. There is a lack of evidence to support a preferred screening regimen in this population, and either tuberculin skin tests (TST) or interferon-γ release assays (IGRAs) are acceptable. Although difficult to assess, the sensitivity of IGRAs and TST are similar (80–95%), while IGRAs are considered to be more specific. METHODS: A 48-year-old White female in rural Iowa with a 30-year history of Crohn’s disease was evaluated for TNF inhibitor therapy. She had no known risk factors for LTBI and was screened using an IGRA which yielded an indeterminate result. A repeat IGRA and a two-step TST were both negative. Subsequently, adalimumab was initiated. Adalimumab was discontinued after 9 months due to progression of Crohn’s, and the patient underwent bowel surgery at a California hospital. Her course was complicated by bilateral pleural effusions requiring thoracentesis twice. RESULTS: The patient presented 1 month later with upper lobe infiltrative changes and mediastinal adenopathy. A third IGRA was performed and was non-reactive. A bronchoscopy with biopsy was then performed. The next day her dyspnea, cough and fevers worsened. She was admitted to an Iowa hospital where she was immediately put in airborne precautions. Her bronchoalveolar lavage acid-fast bacilli (AFB) smear was 4+, and an induced sputum showed 3+ AFB. Standard TB treatment was initiated. At least 59 patients (17 immunocompromised) and five employees in a private office and 13 employees at the Iowa hospital were exposed, in addition to an unknown number in California. CONCLUSION: Although rare, there appears to be a risk for patients on TNF inhibitors who have multiple negative screening tests to become infected with TB. It is unclear whether this represents reactivation of undetected LTBI or new infection, although new TB cases are less likely in rural Iowa where the incidence is 1.53 per 100,000. Patients should be counseled to report any pulmonary symptoms to providers. As demonstrated by this case, airborne precautions should be implemented as soon as possible if clinical suspicion of TB is high despite negative screening tests to reduce exposure to others. DISCLOSURES: All authors: No reported disclosures.