PURPOSE: Quanti-feron TB ®-Gold (QFT-G) is an in vitro diagnostic whole blood assay for tuberculosis (TB) infection using peptide antigens that are associated with M. tuberculosis complex and are absent from all BCG strains and most non-tuberculosis mycobacteria. Thus, a positive QFT-G result is felt to represent TB infection and would be unaffected by a history of previous BCG vaccination. By comparing the percentage of positive QFT-G reactors in persons with and without a history of BCG vaccination, the protective effect of BCG in preventing TB infection in adults can be assessed.
METHODS: During 2006–2007, QFT-G was used as an aid to diagnose TB infection in an out-patient community health center setting among foreign-born adults residing in Suffolk County, New York. All persons receiving QFT-G testing were asked detailed demographic information including history of BCG vaccination.
RESULTS: The overall positivity rate using the QFT-G assay was found to be 13.76% (100/727) as compared to a positive tuberculin skin test (TST) positivity rate of 35.71% (426/1193) in a similar foreign-born adult population. Among persons with a history of BCG vaccination, the QFT-G positivity rate was 14.18% (37/261). Among persons without a history of BCG vaccination the QFT-G positivity rate was 13.52% (63/466).
CONCLUSION: Since there was no significant difference in the rate of TB infection in foreign-born adults with and without a history of BCG vaccination tested for TB infection using QFT-G (which is unaffected by a history of previous BCG vaccination), our results suggest that BCG vaccination offers no apparent protection against TB infection in this foreign-born adult population.
CLINICAL IMPLICATIONS: A history of BCG vaccination seems to offer no apparent protection against TB infection in an adult foreign-born population in Suffolk County, New York.
DISCLOSURE: Lewis Mooney, No Financial Disclosure Information; No Product/Research Disclosure Information