June 2013

Document Type


Degree Name



Dept. of Public Health and Preventive Medicine


Oregon Health & Science University


Intradermal tuberculin skin test has been the traditional means of screening individuals for tuberculosis (TB). Limitations of the TB skin test have necessitated the creation of alternative TB screening tests for low incidence settings. One such screening test is the QuantiFERON-TB Gold© blood test using the Interferon Gamma Release Assay is now used for screening health care workers at the Portland Veterans Administration Medical Center (PVAMC). The PVAMC and other healthcare facilities using this test for serial testing of healthcare workers (HCW) have reported unexpectedly high numbers of positive tests. Upon retesting, a high proportion of these subjects revert back to negative, suggesting their initial test result was a false positive. In the nearly three years since QuantiFERON-TB (QFT) Gold testing began at the PVAMC, approximately six percent of subjects tested positive. This is at least double the proportion of positive TST tests prior to the change to QFT Gold. We hypothesize




School of Medicine



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