Receiver Operating Characteristic (ROC) analysis of selected demographic, smoking and behavioral characteristics associated with lung cancer risk, CR, NANA, and combinations thereof in A) all subjects, and B) European Americans. CR: creatine riboside; NANA: N-acetylneuraminic acid; PPV: Positive Predictive Value; NPV: Negative Predictive Value; risk factors model comprises: age (age at enrollment), education (achieved level of education), income (household income), smoking (smoking status (current-, former-, never-smoker)), pack-years (amount smoked indicated by pack-years), BMI (body mass index), COPD (history of chronic obstructive pulmonary disease), family history of lung cancer.