Predictive factors in smoking cessation with combined therapy with bupropion and nicotine patches

The association of bupropion and nicotine is a good choice in the treatment of smoking cessation. However, not all patients actually give up smoking.

This work was undertaken with the aim of finding out the functional or clinical variables that could be associated with the success of the cessation therapy.

In one year, 88 patients who were treated with bupropion 300 mg/day and nicotine patches were followed-up, for 1 month and 3 months, respectively. They were all questioned about the number of cigarettes per day, the years they have been smoking, the number of quitting attempts, and concurrent pulmonary conditions were sought for. The Fageström Test, forced spirometry (FVC, FEV-1, FEF25-75), and exhaled carbon monoxide (by co-oxymetry) were also assessed. For the statistical analysis, a logistic regression model allowing to predict the response of new subjects to the treatment, with the lowest error possible, was applied. To choose the working model, the highest and lowest value of each variable were found, drawing the correlation matrix between dependent and independent variables, by means of the box-plot procedure. Then, the model's application conditions were analysed: linearity, homoscedasticity, independence of the applications, and normality of the distributions. To assess the discrimination of the model, a ROC curve was used.

Showed that at the end of the follow-up year, 59.1% of the patients quitted smoking. The multivariate analysis with logistic regression showed that no previous history of chronic obstructive pulmonary disease (COPD), a FEF25-75 value and effectively quit after the first week of treatment were independent prognostic factors of treatment success. When the diagnosis precision of our model was analysed by means of the ROC curve, it showed a 78% value, with the 95% confidence interval ranging from 68.5% to 86.9%. At the optimal cut-off point of our model, sensitivity and specificity for quitting smoking were found to be 66.7% and 80%, respectively.

We conclude that with a diagnosis precision of 78.8% patients with no history of COPD, who quitted at the first week of therapy with bupropion and with low FEF25-75, will remain non-smokers after one year follow-up. Contrarily, COPD patients who still smoke after one week of therapy, will not achieve quitting smoking.