Negative effect of smoking on the performance of the QuantiFERON TB gold in tube test
1 Clinical Research Centre, Copenhagen University Hospital Hvidovre, Kettegårds Alle 30, 2650, Hvidovre, Denmark
2 Department of Pulmonary and Infectious Diseases, Copenhagen University Hospital Hillerød, Dyrehavevej 29, Hillerød, 3400, Denmark
3 National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
4 Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Büllowsvej, 1870, Frederiksberg, Denmark
5 National Institute for Medical Research, Muhimbili Medical Research Centre, Dar es Salaam, Tanzania
6 Department of Infectious Diseases, University Hospital, Odense, Sdr. Boulevard 29, 5000, Odense C, Denmark
BMC Infectious Diseases 2012, 12:379 doi:10.1186/1471-2334-12-379Published: 27 December 2012
False negative and indeterminate Interferon Gamma Release Assay (IGRA) results are a well documented problem. Cigarette smoking is known to increase the risk of tuberculosis (TB) and to impair Interferon-gamma (IFN-γ) responses to antigenic challenge, but the impact of smoking on IGRA performance is not known. The aim of this study was to evaluate the effect of smoking on IGRA performance in TB patients in a low and high TB prevalence setting respectively.
Patients with confirmed TB from Denmark (DK, n = 34; 20 smokers) and Tanzania (TZ, n = 172; 23 smokers) were tested with the QuantiFERON-TB Gold In tube (QFT). Median IFN-γ level in smokers and non smokers were compared and smoking was analysed as a risk factor for false negative and indeterminate QFT results.
Smokers from both DK and TZ had lower IFN-γ antigen responses (median 0.9 vs. 4.2 IU/ml, p = 0.04 and 0.4 vs. 1.6, p < 0.01), less positive (50 vs. 86%, p = 0.03 and 48 vs. 75%, p < 0.01) and more false negative (45 vs. 0%, p < 0.01 and 26 vs. 11%, p = 0.04) QFT results. In Tanzanian patients, logistic regression analysis adjusted for sex, age, HIV and alcohol consumption showed an association of smoking with false negative (OR 17.1, CI: 3.0-99.1, p < 0.01) and indeterminate QFT results (OR 5.1, CI: 1.2-21.3, p = 0.02).
Cigarette smoking was associated with false negative and indeterminate IGRA results in both a high and a low TB endemic setting independent of HIV status.