Quantiferon-Gold (QFT-G) is a whole-blood interferon-gamma release assay which is FDA-approved for detection of M. tuberculosis infection. Recent CDC guidelines have suggested that this test could be used in place of the PPD for testing of health care workers (HCW) (1, 2). In October, 2006, Beth Israel Deaconess Medical Center (BIDMC, Boston, MA), in collaboration with the Massachusetts State
... [Show full abstract] Laboratory Institute TB laboratory, began routinely testing all PPD+ (≥10 mm induration) newly hired employees with QFT-G to aid in diagnosis of latent tuberculosis infection (LTBI). This algorithm was designed to take advantage of the high specificity of QFT-G to determine which PPD+ new employees needed further clinical follow-up and potential LTBI therapy. After three months of testing, a quality assurance review of all clinical and QFT-G data was performed. Our goal was to evaluate the proportion of positive and negative QFT-G results in our employee population, and in particular in those employees felt to be at the highest clinical risk for having LTBI. Introduction. Quantiferon-Gold (QFT-G) is FDA-approved for diagnosis of infection with M. tuberculosis. CDC guidelines have supported the use of QFT-G for routine TB screening of health care workers (HCW) and have suggested that QFT-G could be used in place of the PPD. Our goal was to evaluate the proportion of positive and negative QFT-G results in PPD-positive HCW at a large American medical center, particularly in those who were felt to be at highest clinical risk for having LTBI. Abstract 26 (18%)115 (81%)2 (1%) 23 (28%)57 (70%)2 (2%) A. Quantiferon-Gold (QFT-G) test results for 143 PPD+ (!10 mm induration) newly-hired HCW tested as part of a new hospital TB screening algorithm. Approximately 93% reported a definite or probable history of BCG vaccination. B. Of the 143 HCW tested, 115 had sufficient clinical information available to allow LTBI risk classification; 82 of the 115 were classified as high clinical risk for LTBI by our criteria. Of these 82 high LTBI risk individuals, 57 (70%) tested negative, suggesting that their QFT-G test results could be false negatives. 24 of the 115 clinically evaluable HCW (21%) tested positive by QFT-G and 23/24 were in the high LTBI risk group (the remaining individual had a 24 mm PPD but spent much of his life in Iran, an area of intermediate TB endemnicity (13/100,000) according to our resource table.) b LTBI: latent tuberculosis infection
