Biomarker-based assessment of tobacco smoke exposure in Saudi females via analysis of urinary cotinine level

Tobacco smoking remains a leading preventable cause of morbidity and mortality worldwide. In Saudi Arabia, cultural stigma and reliance on self-reported data obstruct precise assessment of female smoking prevalence and second-hand smoke exposure. Urine cotinine, a stable metabolite of nicotine is a well-established objective biomarker for assessing both active and passive tobacco exposure. The current study aimed to: (1) assess tobacco smoke exposure among Saudi females by combining questionnaire data with biomarker measurements, (2) validate an LC-MS/MS method for quantifying urinary cotinine and (3) establish population-specific cutoff values to distinguish smokers and nonsmokers (4) analyse smoking behaviours and influencing factors via a survey questionnaire. A cross-sectional design was employed involving 133 Saudi female participants recruited between May and December 2024. Each provided a urine sample and completed questionnaire on smoking behaviour and second-hand smoke exposure. Urine samples were processed and analysed by LC-MS/MS. Method validation followed ICH-M10 guidelines, assessing linearity (2–500 ng/mL), accuracy (90–107%) and precision (CV < 10%). The method exhibited excellent linearity (R 2 ≥ 0.9992). Urinary cotinine was detected in 48 of 133 samples, with concentrations ranging from 0.02 to 7.693 ng/mL. Despite 88.7% of participants self-reporting as nonsmokers, 45.9% reported household second-hand smoke exposure. A cutoff value of 7 ng/mL was established to distinguish smokers from nonsmokers based on ROC analysis. Urinary cotinine, quantified by a validated LC-MS/MS method, provides a reliable and objective assessment of tobacco exposure among Saudi females. This approach addresses the limitations of self-reported data and supports the development of targeted public health interventions aimed at reducing active smoking and second-hand smoke exposure in this population.