infectious diseases

Bacteria Mycobacterium tuberculosis

The project demonstrated that bringing testing in-house will decrease turnaround time and cost, and increase the populations that can be tested by IGRA.

Latent TB infections, representing the remainder of the“ iceberg,” can be difficult to identify as the bacteria are present in the body yet inactive. Additionally, the person does not exhibit symptoms and they cannot spread the bacteria to others. However, a latent TB infection may develop into an active case at any time; one study suggested that approximately 80 % of all active TB cases in the United States arise from latent TB infection. 3, 4

The next step in public health’ s effort to eliminate TB in the United States is to better identify and track latent TB infections. As an early step in that effort, APHL selected 11 sites to receive awards aimed at expanding public health access to the interferon gamma release assay( IGRA), a test used to detect TB infection.

The two diagnostic tests commonly used to detect TB infection are the tuberculin skin test( TST) and IGRA. Both have limitations including the interpretation of the test, the populations that should receive that test, and how the testing is executed. However, use of IGRA has advantages that make it desirable, including a one-time visit and lack of false reactivity due to previous BCG vaccination. Unlike TST, IGRA is a laboratory-based test requiring special equipment and adherence to strict sample processing and handling

requirements that can make implementation challenging in a public health setting. In order to expand access to the use of IGRAs, APHL, in partnership with CDC, solicited applications from public health laboratories and their related jurisdictional TB control programs to bring on or expand their testing for TB infection using this method.

The selected sites began work on their IGRA expansion proposals in January 2016 and completed work in September 2016. Collectively, participating sites reported at least 100 newly trained laboratory and clinical staff qualified to perform steps associated with IGRA, decreased turnaround time( TAT) by an average of three days from previous IGRA TATs, and a 104 % increase in overall IGRAs performed. As a result of the project, two sites were able to expand their IGRA testing program within correctional facilities located within their state by increasing the number of inmates screened, representing a large advantage in identifying latent TB infection among an inherently high-risk population.

One particularly encouraging result of the project was that a participating site that had been utilizing a third party for IGRA testing moved their testing program in-house after completing the project. The project demonstrated that bringing testing in-house will decrease turnaround time and cost, and increase the populations that can be tested by IGRA. The project also increased cooperation and collaborations between laboratory and programmatic staff as both parties worked closely for the project’ s duration. While a complete evaluation of the project has not yet been completed, early indications are that the project was a success in the expansion of the use of IGRA in the fight to uncover more of the TB iceberg. Further evaluations will focus on whether expanded access had the broader goal of preventing TB disease by ensuring persons with TB infection are offered and complete treatment.

Bacille Calmette-Guerin( BCG) is a vaccine for TB disease. Many foreign-born persons have been BCG-vaccinated. BCG is used in many countries with a high prevalence of TB to prevent childhood tuberculous meningitis and miliary disease.

References 1. Centers for Disease Control and Prevention( CDC). Reported Tuberculosis in the United States, 2015. Atlanta, GA; US Department of Health and Human Services, CDC: 2016. Available at: https:// www. cdc. gov / tb / statistics / reports / 2015 / pdfs / 2015 _ surveillance _ report _ fullreport. pdf 2. Miramontes R, Hill AN, Yelk Woodruff RS, Lambert LA, Navin TR, Castro KG, LoBue PA. Tuberculosis Infection in the United States: Prevalence Estimates from the National Health and Nutrition Examination Survey, 2011-2012. Plos One 2015 Nov

4; 10( 11) e0140881. 3. Shea KM, Kammerer JS, Winston CA, Navin TR, Horsburgh CR Jr. Estimated Rate of Reactivation of Latent Tuberculosis Infection in the United States, Overall and by Population Subgroup. Am J Epidemiol 2014 Jan 15:179( 2): 216-25. 4. Yuen CM, Kammerer JS, Marks K, Navin TR, France AM. Recent Transmission of Tuberculosis— United States, 2011-2014. PLoS One. 2016 Apr 15; 11( 4): e0153728.