577. Challenges of Utilizing Interferon Gamma Release Assay in Investigation of Contacts of a Healthcare Provider with Active Tuberculosis
Session: Poster Abstract Session: Mycobacterial Diagnostics
Friday, October 21, 2011
Room: Poster Hall B1

Challenges of Utilizing Interferon Gamma Release Assay in Investigation of Contacts of a Healthcare Provider with Active Tuberculosis

Background: The Centers of Disease of Disease Control and Prevention recommends the use of interferon gamma release assay (IGRA) in all situations where a tuberculin skin test is used. In August 2010, a newly employed physician was diagnosed with smear negative cavitary pulmonary tuberculosis (TB) in a cancer center of a medical facility in North Dakota where the TB incidence rate is only 0.8 per 100,000 in 2009. We describe the process of our contact investigation using the T cell assay.

Methods: A review of the electronic medical records identified patients who were exposed to the physician index case. Immunosuppressed patients were highest priority and were referred to infectious disease (ID) for evaluation. Family members were encouraged to identify possible exposure if they were present with their family during healthcare visits or hospitalizations. IGRA was obtained at baseline and again after 8 weeks of exposure.

Results: A total of 109 patients and patient relatives among 130 exposed individuals underwent IGRA [Figure]. Up to 14 (13%) of patients had an indeterminate initial test. IGRA misclassified two patients with known history of latent TB infection as converters. Two converters who had a low risk contact with the physician index case had an initial conversion then a third test showed regression.

Conclusion: Although IGRA testing was successfully implemented in our active tuberculosis contact investigation, indeterminate results and regression of converters made interpretation of results challenging. This has to be done with caution considering the right clinical scenario and level of exposure. Our practical experience in utilizing IGRA may guide other institutions who could be faced with similar challenges in TB contact investigations.

Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

Joan Cook1, Augusto Alonto1,2, Paul Carson1,2, Gino Tapia-Zegarra1,2, Michael Trythall3 and Dubert Guerrero1,2, (1)Sanford Health, Fargo, ND, (2)University of North Dakota School of Medicine and Health Sciences, Fargo, ND, (3)North Dakota Public Health Laboratory , Bismarck, ND


J. Cook, None

A. Alonto, None

P. Carson, None

G. Tapia-Zegarra, None

M. Trythall, None

D. Guerrero, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.