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Screening Health Care Workers With Interferon-γ Release Assay Versus Tuberculin Skin Test: Impact on Costs and Adherence to Testing (the SWITCH study)

Wrighton-Smith, Peter MEng, PhD; Sneed, Laurie AA; Humphrey, Frances MSN; Tao, Xuguang MD, PhD; Bernacki, Edward MD, MPH

Journal of Occupational and Environmental Medicine: July 2012 - Volume 54 - Issue 7 - p 806–815
doi: 10.1097/JOM.0b013e318254620f
Original Articles: CME Available for this Article at

Objective: To determine the price point at which an interferon-γ release assay (IGRA) is less costly than a tuberculin skin test (TST) for health care employee tuberculosis screening.

Methods: A multidecision-tree based cost model incorporating inputs gathered from time–motion studies and parallel testing by IGRA and TST was conducted in a subset of our employees.

Results: Administering a TST testing program costs $73.20 per person screened, $90.80 per new hire, and $63.42 per annual screen. Use of an IGRA for employee health testing is cost saving at an IGRA test cost of $54.83 or less per test and results in higher completion rates because of the elimination of the need for a second visit to interpret the TST.

Conclusions: Using an IGRA for employee health screening can be an institutional cost saving and results in higher compliance rates.

Supplemental Digital Content is available in the text.

From Oxford Immunotec Ltd (Dr Wrighton-Smith), Abingdon, United Kingdom; Health, Safety and Environment (Occupational Health Services) (Ms Sneed, Ms Humphrey, and Dr Bernacki), The Johns Hopkins Health System and University, Division of Occupational and Environmental Medicine (Drs Tao and Bernacki), Johns Hopkins University School of Medicine, and Department of Epidemiology (Dr Tao), Johns Hopkins University Bloomberg School of Public Health, Baltimore, Md.

Address correspondence to: Edward Bernacki, MD, MPH, Johns Hopkins University, School of Medicine, 600 N. Wolfe Street, Billings Administration 129, Baltimore, MD 21287 (

Oxford Immunotec contributed to the study by processing tests free-of-charge for those people entering the study and receiving an IGRA in addition to their usual TST. In addition, Oxford Immunotec provided an educational grant to Johns Hopkins University of $49,300 to provide a contribution toward the additional resources that were necessary to hire to undertake the study (eg, for conducting phlebotomy after the TST in screening sessions). Johns Hopkins contributed to the study by providing the time of their regular Employee Health staff free-of-charge to complete the study. No Johns Hopkins staff member has received any remuneration of any kind from Oxford Immunotec. Dr Wrighton-Smith is an employee of Oxford Immunotec.

Edward Bernacki and coauthors have no relationships/conditions/circumstances that present potential conflict of interest.

The JOEM Editorial Board and planners have no financial interest related to this research.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (

©2012The American College of Occupational and Environmental Medicine