High rate of negative results of tuberculin and QuantiFERON tests among individuals with a history of positive skin test results.

Objectives: To evaluate individuals at high risk for tuberculosis exposure who had a history of a positive tuberculin skin test (TST) result in order to determine the prevalence of unsuspected negative TST results. To confirm these findings with the QuantiFERON-TB test (QFT), an in vitro whole-blood assay that measures tuberculin-induced secretion of interferon-gamma.

Methods: This survey was conducted from November 2001 through December 2003 at 3 sites where TST screening is regularly done.