Validation of Urinary Thiocyanate as a Robust Biomarker of Active Tobacco Smoking in the Prospective Urban and Rural Epidemiological Study.

This article focuses on evaluating urinary thiocyanate as a biomarker of active tobacco smoking across diverse populations from 14 countries in the Prospective Urban and Rural Epidemiological (PURE) study. Urinary thiocyanate, a metabolite of cyanide exposure from tobacco smoke, showed a strong dose–response correlation with daily cigarette consumption and total nicotine equivalents, outperforming urinary cotinine in distinguishing smokers from never-smokers. The study established region-specific cutoff values for urinary thiocyanate that varied by country income level—high-, middle-, and low-income countries—reflecting differences in smoking behaviors, cigarette products, and dietary intake of goitrogenic foods, which also contributed to background thiocyanate levels in never-smokers. While urinary thiocyanate effectively differentiated active smokers, it was not sensitive to secondhand smoke exposure. The findings suggest urinary thiocyanate is a cost-effective, stable biomarker for assessing tobacco smoke exposure internationally, with implications for improving the accuracy of smoking status classification in epidemiological research.