Fagerstrom Test and Heaviness Smoking Index. Are they Interchangeable as a Dependence Test for Nicotine?

Objective: The purpose of this study was to evaluate the degree of agreement between the Fagerstrom Test for Cigarette Dependence (FTCD) and the Heaviness of Smoking Index (HSI) in daily smokers admitted to smoking cessation clinics from National Healthcare System in Spain and Argentine Republic. Material and methods: An observational, longitudinal, multicenter study (prospective cohort) conducted in smoking clinics in daily clinical practice. The patients were consecutively included as they attended the consultations. The statistical analysis was descriptive, and correlation and concordance tests as well as analysis and regression models were used. Results: In total, 308 subjects were included [161 women (52.3%)], with a mean age of 51.4 (10.8) years. We found an absence of agreement and the existence of a proportional difference between both tests [Regression coefficient for global series: 0.55 (0.52-0.59) p < .001]. This difference increased as the value of the FTCD score increased; that is, the higher the value of the FTCD score was, the greater the difference in relation to the value of the HSI score. Likewise, Cohen's kappa concordance coefficient, according to various combinations of categorization of both tests, showed that the agreement between these variables was only good. Approximately 20% of the subjects were not classified with the same degree of dependence by the two tests. Thus, a classification mismatch existed. Conclusions: We found an absence of agreement between both tests. These data imply that we should not substitute one test for the other when we analyze nicotine dependence in a population of smokers.