Consistency of Biomarkers of Exposure in the Population Assessment of Tobacco and Health Study from Samples Taken 3 to 5 Years Apart.

Introduction: Urinary biomarkers are useful in characterizing exposure to harmful and potentially harmful constituents (HPHCs) of tobacco products and linking exposure to health outcomes. However, the consistency/reproducibility of many urinary biomarkers over long periods is unknown.

Methods: Among people who exclusively used cigarettes in the Population Assessment of Tobacco and Health Study Waves 1, 2, 4, and 5 (ranging from 746 to 1361 subjects), we used weighted models to estimate variance components and intra-class correlation coefficients (ICC) for 15 biomarkers of exposure for urine samples collected 3-5 years apart, creatinine-only-adjusted and also adjusted for demographic and behavioral predictors.

Results: In models adjusted only for creatinine, ICC values of biomarkers ranged from 0.41 (95% confidence interval (CI): 0.32, 0.49) (N-acetyl-S-(2-carbamoylethyl)-L-cysteine) to 0.73 (95% CI: 0.65, 0.81) (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol), varying within each chemical class. For models adjusted for predictors, associations between biomarkers and predictors were similar for samples collected 3-5 years and 1 year apart. Predictor-adjusted ICCs for samples collected 3-5 years apart ranged from 0.29 (95% CI: 0.17, 0.40) (N-Acetyl-S-(2-carbamoylethyl)-L-cysteine) to 0.63 (95% CI: 0.56, 0.69) (N-Acetyl-S-(2-hydroxyethyl)-L-cysteine) and appeared not different from those for samples collected 1 year apart.

Conclusions: Even for 3 or 5 years between urine sample collection, unadjusted biomarkers of exposure showed fair to excellent reproducibility. Similar consistency between 1 year and 3-5 years between collections was found when including predictors in the model.

Implications: These biomarkers may be useful to characterize long-term exposures to HPHCs from cigarettes with different characteristics for those who smoke cigarettes exclusively.