Validity assessment of self-reported smoking status to detection of urine cotinine levels among patients with tuberculosis undergoing tobacco cessation treatment

Abstract

Introduction and Aim: Tobacco cessation programs by and large use self-reporting as the gold standard for assessing tobacco use. However, self-reporting may be skewed due to the socio-demographic profile and the context in which the respondents share their tobacco history after undergoing tobacco cessation treatment. It is therefore, imperative to validate the respondents’ self-reported smoking status in an effective manner. Hence, this study aimed in validating the self-reported smoking status of study participants with their urine cotinine levels in a randomized controlled trial on smoking cessation. Materials and Methods: A cross-sectional study was conducted in Dakshina Kannada district of Karnataka to validate the self-reported smoking status of 300 participants. A seven-day point prevalence of smoking status was assessed based on a questionnaire and validated further using the semi-quantitative urine cotinine test at the end of a randomized smoking cessation study. Results: The sensitivity and specificity of self-reported smoking status was 73.17% and 95.79% respectively. Other validity indicators like positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, and accuracy were estimated to be 97.40%, 62.33%, 17.38%, 0.28%, and 80.33% respectively. Cohen’s kappa statistics showed a substantial agreement (k=0.61; SE= 0.04) between the two test methods. Educational status and the level of motivation to quit showed a significant association between the test methods. Conclusion: Self-reported smoking status of participants is not sensitive in identifying smokers thus leading to under-reporting.