Basically it proves the hypothesis that those who are TST+ and QFT- do not need to be treated for LTBI.
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Abstracts from the
26th International Congress of Chemotherapy and Infection
“The Changing Climate of Infectious Diseases”
“The Changing Climate of Infectious Diseases”
INCORPORATING THE AMMI CANADA CACMID ANNUAL CONFERENCE 2009
18 21 June 2009
Toronto, Canada • Sheraton Centre Toronto Hotel
International Society of Chemotherapy for Infection and Cancer
www.ischemo.org
18 21 June 2009
Toronto, Canada • Sheraton Centre Toronto Hotel
International Society of Chemotherapy for Infection and Cancer
www.ischemo.org
The predictive utility of a negative QuantiFERON-TB Gold test in the development of active tuberculosis
W. Chan1 *, E. Der2, G. Tyrrell1, D. Kunimoto1.
1University of Alberta, Edmonton, Canada,
2Alberta Health Services, Edmonton Region, Edmonton, Canada
Objectives: The QuantiFERON-TB Gold (QFT) test is an assay measuring the amount of interferon-gamma secreted from lymphocytes after stimulation by antigens of M. tuberculosis. Locally, it is used in the setting of patients who are tuberculin-skin test (TST) positive to help decide whether or not to treat these patients for latent tuberculosis infection (LTBI). Our objective was to determine whether patients with a positive TST but negative QFT result developed active tuberculosis if they went untreated for LTBI.
Methods: A retrospective review was conducted of the QFT tests conducted through the Edmonton TB Program from Nov. 1, 2004 to Oct. 31, 2007. Of these, patients that tested positive by TST but negative by the QFT assay were identified, then categorized by whether or not they had received LTBI treatment. This list was then compared to a list of all Alberta patients that developed active tuberculosis from Nov. 1, 2004 to Oct. 31, 2008.
Results: 1853 QFT tests on 1752 patients were reviewed. 1430 were TST positive. 823 of these also had a negative QFT test (57.6%). 97 received LTBI treatment, leaving 726 untreated. 1849 patient years of follow-up were obtained, the minimum follow-up being one year, and the mean and median being 2.5 years. Two cases of active tuberculosis were identified in these 726 patients during this follow up period. Chart review indicated that these two QFT tests were both done in the setting of active pulmonary tuberculosis.
Conclusion: Patients who are TST positive and QFT negative are unlikely to develop active tuberculosis as a result of reactivating LTBI even in the absence of LTBI therapy, at least in the short term.
