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System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis
Published on: April 5, 2017
Screening for Mycobacterium tuberculosis using an interferon-gamma release assay
Terri Simpson1, Joyce Fox, Karen Crouse
1University of Washington School of Nursing, Seattle, WA, USA. tsimpson@uw.edu
Insights
Interferon-gamma release assays (IGRAs) are used for tuberculosis screening. Community health centers showed the highest positive IGRA rates, indicating their importance in targeted screening programs.
Area of Science:
- Public Health
- Infectious Disease Epidemiology
- Clinical Diagnostics
Background:
- Centers for Disease Control and Prevention recommend analyzing Mycobacterium tuberculosis infection screening using interferon-gamma release assays (IGRAs).
- IGRAs are increasingly utilized for tuberculosis (TB) screening.
Purpose of the Study:
- Characterize IGRA test requests at the first Washington State laboratory offering the assay.
- Document the implementation process of IGRA testing in a public health setting.
Main Methods:
- Retrospective record review of 4422 IGRA requests from 4218 unique subjects (2008-2009).
- Analysis included IGRA results, request source, reasons for testing, demographics, risk factors, and prior TB exposure.
- Examined Tuberculin Skin Test (TST) induration sizes in relation to IGRA results.
Main Results:
- Most IGRA requests (96%) originated from public health clinics, hospitals, private practitioners, and Indian Health Centers.
- Community and migrant health centers exhibited the highest positive IGRA rates (28%).
- Approximately 50% of requests were for employment or high-risk surveillance.
Conclusions:
- Public and private entities utilize IGRAs for surveillance of various populations, including those employed, at high risk, or foreign-born.
- Significant variation in TST induration was observed for individuals with indeterminate IGRA results.
- The program's implementation process can serve as a model for other IGRA analysis reviews.
Context:
The Centers for Disease Control and Prevention recommend analyzing characteristics of populations screened for Mycobacterium tuberculosis infection using interferon-gamma release assays (IGRAs).
Objective:
We characterized requests for IGRA analyses submitted to the first laboratory in Washington State that began to offer IGRAs as a tuberculosis screening test. In addition, we chronicled the process by which this program was launched.
Design:
Through a retrospective record review we recorded the IGRA results, source of the request, and reason(s) for each request along with demographic information, risk factors, and prior exposure for each subject. Through dissemination and quality control measures, IGRA analyses began within the health district but quickly spread throughout the state and the West.
Setting And Participants:
A regional health district clinical laboratory in the Pacific Northwest received 4422 IGRA requests for 4218 unique subjects from January 2, 2008, through June 5, 2009.
Results:
Most (96%) requests originated from public health clinics or centers, hospitals, private laboratories or practitioners, and Indian Health Centers. Community and migrant health centers had the highest rates of positive IGRA results (28%, Φc = 0.159, P = .000). About one-half of all requests were for employment or high-risk surveillance. Persons with a positive IGRA had a larger TST induration (M = 16.66 mm, 95% CI: 15.18-18.14) than those with a negative IGRA (M = 13.53 mm, 95% CI: 12.92-14.15) but did not differ for those with an indeterminate IGRA (M = 13.29 mm, 95% CI: 5.95-20.62).
Conclusions:
Public and private agencies use IGRAs for surveillance of persons employed, routinely screened, at high risk, or foreign-born. The TST induration varies widely for persons with an indeterminate IGRA. The process for implementing IGRA analyses serves as a model for other programs seeking to conduct similar reviews of test use and results.
