Using Newer Interferon Gamma Release Assays in the Indian Health Service as Part of a Comprehensive Targeted Testing Program for Latent Tuberculosis Infection among American Indians & Alaskan Natives Classified as High-Risk for Progression to Active Stage TB Disease

Latent tuberculosis infection (LTBI) is a silent threat to public health, nationwide, and addressing it remains a challenge. The Centers for Disease Control and Prevention (CDC) announced its Total TB Elimination Goal in 1989 with a target year of 2010 for the eradication of tuberculosis from the United States. Although TB rates have steadily declined over the last decade, the rate of decline is slowing every year (CDC, 2008). To reach this goal, all federal agencies will have to work together to design and implement effective screening programs. Improvements in the specificity of available testing methods hold one part of a national solution to TB elimination. Many state public health departments have already implemented TB programs which not only embrace these newer test methodologies, but also rely on targeted testing models for latent tuberculosis infection among special populations deemed to be at increased risk for the development of active TB disease. The Indian Health Service is lagging behind its peers in adequately addressing latent tuberculosis among Native Americans. By developing targeted screening programs for high-risk American Indians/Alaskan Natives which incorporate interferon gamma release assay methodologies for a more accurate diagnosis of infection, the disease disparity that exists for tuberculosis among AI/AN's can be effectively reduced. The financial cost of running such programs would be offset by the health benefit of disease prevention among AI/AN's and the associated reduction in health care expenditures to treat both infection and disease. Although persons with LTBI cannot transmit TB disease to others, they harbor the etiologic agent of TB, Mycobacterium tuberculosis. In the report "Ending Neglect" (2000), the Institute of Medicine (IOM) stated that any individual with LTBI is at increased risk for developing active TB disease and thereby entering an infectious state in which they can transmit the disease to others (p.16). Progression from LTBI to active disease carries a risk of 10% over the lifetime of the individual, with further increased risk found among immunocompromised groups (CDC, 2010b). Progression from latent infection to active disease is the result of a compromised immune system response to infection. Compromised immunity occurs through a variety of pathways including, but not limited to, the development of autoimmune diseases (i.e. rheumatoid arthritis, lupus erythematosis, scleroderma etc ... ); the onset of cancer (particularly lung and bronchus); HIV infection; pharmacologic immune suppression; health conditions such as diabetes mellitus and chronic renal failure; and health behaviors such as smoking and drug abuse (CDC, 2010a). Native Americans form a unique high-risk group due in part to their ethnicity where there exists a higher genetic predisposition to the development of some immunocompromising diseases. Native Americans are also victim to many multifactoral health disparities which subsequently lead to increased rates of conditions and behaviors that weaken the immune system. Therefore, a new and more effective approach is required to adequately screen, accurately diagnose, and properly manage the treatment of American Indian and Alaskan Native (AI/AN) patients receiving care through Indian Health Service clinics nationwide. Utilizing newer Interferon Gamma Release Assays (IGRA), such as T. Spot TB and Quantiferon TB Gold In Tube, in Indian Health Service laboratories to target AI/ AN's classified as "high risk" for progression of LTBI to active tuberculosis will increase patient compliance with testing, decrease the incidence of cross reactivity reactions, and more accurately identify infection in immunocompromised AI/AN's. The cost savings over time is demonstrated to be significant thereby substantiating a transition to IGRA screening for Latent TB Infection at all federally funded facilities.