Accuracy of self-reported smoking status in adult survivors of childhood cancer: A report from St. Jude Lifetime Cohort study.

Abstract

10570 Background: Although clinicians often evaluate smoking behavior in cancer survivors via self-report, the validity of this approach is unknown. We validated self-reported smoking status by serum cotinine data in clinically assessed adult survivors of childhood cancer and identified factors contributing to misclassification. Methods: The study sample consists of 287 randomly selected adult survivors of childhood cancers participating in the St. Jude Lifetime Cohort Study and undergoing a risk-based clinical assessment in a survivorship clinic. Self-reported smoking status was classified as never (N = 105), past (N = 111), and current (N = 71) smokers. Age, sex, and race/ethnicity were balanced among the three groups (p’s > 0.05). Blood samples were obtained and serum cotinine levels were quantified by liquid chromatography tandem mass spectrometry. Misclassification was determined by the discrepancies between self-reported smoking status and race/ethnicity-specific serum cotinine thresholds (Benowitz et al. Am J Epidemiol 2009). Multiple logistic regression model was used to identify factors related to misclassification. Results: Of the 287 survivors (mean age = 34 years [range = 19-61]; mean time from diagnosis = 24 years [range = 11-46]), 55.4% were male and 84.0% non-Hispanic white. Cotinine levels consistent with recent active smoking were present in 39.4% compared to 24.7% who self-reported as being a current smoker (X2= 14.1; p = 0.0002). Rates of misclassification were 36.9%, 8.4%, and 6.7% in survivors who reported themselves as past, current, and never smokers, respectively. Among self-reported past smokers, 18-30 years of age at survey, male, and current marijuana use increased the risk of misclassification: RR = 3.0 (95%CI = 1.2-7.6), 2.5 (95%CI = 1.1-5.4) and 3.2 (95%CI = 1.1-9.3), respectively. Conclusions: Within a clinical setting, reliance on self-report of smoking status by survivors results in a high misclassification rate. For research, serum cotinine levels should be utilized to assign smoking status. For clinical care and health promotion, clinicians need to be aware of the high rate of misclassification when relying upon self-reported smoking status.