Assessment of the influence of direct tobacco smoke on infection and active TB management.

BACKGROUND: Smoking is a risk factor for tuberculosis (TB) infection and disease progression. Tobacco smoking increases susceptibility to TB in a variety of ways, one of which is due to a reduction of the IFN-γ response. Consequently, an impaired immune response could affect performance of IFN-γ Release Assays (IGRAs). OBJECTIVE: In the present study, we assess the impact of direct tobacco smoking on radiological manifestations, sputum conversion and immune response to Mycobacterium tuberculosis, analyzing IFN-γ secretion by IGRAs. METHODS: A total of 525 participants were studied: (i) 175 active pulmonary TB patients and (ii) 350 individuals coming from contact tracing studies, 41 of whom were secondary TB cases. Clinical, radiological and microbiological data were collected. T-SPOT.TB and QFN-G-IT were processed according manufacturer's instructions. RESULTS: In smoking patients with active TB, QFN-G-IT (34.4%) and T-SPOT.TB (19.5%) had high frequencies of negative results. In addition, by means of an unconditional logistic regression, smoking was a main factor associated with IGRAs' false-negative results (aOR: 3.35; 95%CI:1.47-7.61; p<0.05). Smoking patients with active TB presented a high probability of having cavitary lesions (aOR: 1.88; 95%CI:1.02-3.46;p<0.05). Mean culture negativization (months) ± standard deviation (SD) was higher in smokers than in non-smokers (2.47±1.3 versus 1.69±1.4). Latent TB infection (LTBI) was favored in smoking contacts, being a risk factor associated with infection (aOR: 11.57; 95%CI:5.97-22.41; p<0.00005). The IFN-γ response was significantly higher in non-smokers than in smokers. Smoking quantity and IFN-γ response analyzed by IGRAs were dose-dependent related. CONCLUSIONS: Smoking had a negative effect on radiological manifestations, delaying time of sputum conversion. Our data establish a link between tobacco smoking and TB due to a weakened IFN-γ response caused by direct tobacco smoke.

Harm reduction--a treatment approach for resistant smokers with tobacco-related symptoms.

Smokers with chronic obstructive pulmonary disease (COPD) appear to represent a hard-core group, and this presents a dilemma for chest physicians. A reduction in cigarette smoking benefits health, and nicotine replacement therapy (NRT) can aid smoking reduction. Hence we studied the efficacy of nicotine gum in helping hard-core smokers with severe COPD to quit. Seventeen smokers with severe COPD (FEV(1) 38-47% of predicted normal) who smoked >30 cigarettes/day but were unable to quit were encouraged to reduce their smoking as much as possible by using 4-mg nicotine gum. Five gradually reduced their daily tobacco consumption and, 18 months after starting NRT, were smoking an average of 6 cigarettes/day while still using nicotine gum. Compared to baseline, their respiratory symptoms had improved, and both FEV(1) and FVC had increased. There was no improvement in pulmonary function in the group of smokers who did not reduce their cigarette consumption. No adverse events relating to nicotine occurred among the patients who used NRT to reduce their smoking. We propose that this reduction approach should be considered for patients with respiratory disease who are unable or unwilling to stop smoking.

Atención y prestación de servicios en materia de tabaquismo / Tobacco addiction: care and services

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