Evaluation of spot urine as an alternative to 24 h urine collection for determination of biomarkers of exposure to cigarette smoke in adult smokers

• Biomarkers of cigarette smoke exposure were measured in spot urine.
• Samples were collected at different times of the day for 3 days.
• The spot urine levels were validated against the 24 h urine collection.
• Daily smoke exposure can be best estimated from early morning spot urine.

ObjectiveExposure to cigarette smoke in adult smokers (SM) can be determined by measuring urinary excretion of selected smoke constituents or metabolites. Complete 24 h urine collections are difficult to achieve in ambulatory clinical studies; therefore spot urine (SU) might be a useful alternative. The objective of this study was to evaluate the optimum time for SU collections, and to predict 24 h urine biomarker excretion from SU collections.MethodsSU samples were collected at three time points (early morning, post-lunch and evening) along with 24 h collections in 37 healthy adult smokers. Nicotine and its five metabolites (nicotine equivalents, NE), metabolites of NNK (NNAL), pyrene (1-OHP), acrolein (HPMA), benzene (S-PMA) and butadiene (MHBMA) were measured in 24 h and SU samples. Correlation and agreement between creatinine-adjusted SU and 24 h urine collections were determined from the Pearson product-moment correlation, Bland–Altman and Lin’s concordance correlation analyses. A random effect regression model was used to calculate the 24 h biomarker excretion from SU collections.ResultsThere were no significant differences (p > 0.05) between the three SU collections for the selected biomarkers of exposure except for 3-HPMA, which showed a diurnal variation. Good correlation and statistical agreements were observed for creatinine-adjusted SU (all three time points) and 24 h for most of the selected biomarkers. 24 h biomarker excretion could be estimated for most of the biomarkers based on the regression model, with the early morning SU collections giving the best results for tobacco specific biomarkers NE (R2 = 0.66) and NNAL (R2 = 0.6).ConclusionsSU is a useful alternative to 24 h urine collections for most of the selected biomarkers of exposure to cigarette smoke. The early morning SU appears to be the most feasible and practical option as an alternative to 24 h collections.